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Welcome to the New Section: Instrumentation and Equipment

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Richard Berry
Richard Berry's picture
Welcome to the New Section: Instrumentation and Equipment

I've agreed to be the leader of the new Instrumentation and Equipment section, and I have asked Bob Massey, Arne Hendon, Gary Walker, and George Silvis to serve a resource persons. I am sure that we will welcome more as time goes on. I am just getting my head around what will be involved. The section will operate in coordinate with this Forum section of the same name. Thoughts from any/all of you are most welcome. I am here as a generalist and make no claim to expertise in any body of knowledge or best practices.

We all recognize that the science of astronomy depends intimately on the instruments (photometers, spectroscopes, etc.) and equipment (telescopes, mounts, and gadgetry). We all depend on these things, but there has never been a central locus for talking about them. The section will be devoted to learning about, using, and inventing both instruments and equipment. Our "charge" will clearly include CCDs, CCD cameras, CMOS, telescopes, mounts, computer controls, observatories, observatory systems, software, accessories, and whatever else we may dream up.

Broadly, I think we'll have three areas of operation:

  1. Advice or best practices in fairly established areas, such as "what to look for in a CCD camera." Perhaps we will accomplish this through short documents, videos, or and other instructional media.
  2. A growing collection of novel project write-ups that are "completed" and written up as "The Sliski Weather Monitor," or "The Windy River Observatory."
  3. Serving as a platform in developing "maker" areas such as printed spectroscopes, building a spectrum-balanced flat-box, and/or software. When a project matures and becomes a done thing, we would archive it in #2).

For example, I am in the process of making a "dark box/light box" that sits just south of my telescope about an inch from the end of the tube. The dark box is a deep box painted black inside with black velvet at the back. When the telescope is west of the pier and pointed at alt=0, az=180, it looks into the black box. On the east side of the pier at alt=0, az=180, it looks at the flat box. Simple with no moving parts.

Welcome aboard,

Richard Berry

Richard, thankyou for

Richard, thankyou for volunteering.  I am looking forward to a busy and interesting forum.

After I think about your light box, I may have a couple of questions.

Jim Jones

Ed Wiley_WEY
Ed Wiley_WEY's picture
Great idea

Great idea, Richard. Many thanks for steping up. I am especially interesed in light box solutions. Right now I have an LED panel that has extra near IR bulbs for my Ic filter. I am not convenced that it is yielding totally flat flats and am always looking for alternatives in the 14"-16" size and remote operation capability.


spp's picture
Computer monitor screen for flats

I have just been in touch with a former CCD class student who has been experimenting with using a monitor screen as a light panel for making flats.  He sent me the attached fits image of his master flat.  The scope is an 8 in. F/4 newtonian.  The camera is an ST-8xe.  We are discussing how he can test this flat.  

Does anyone else have experience using a computer monitor as an EL flat panel?



Richard Berry
Richard Berry's picture
Computer monitor for flats

Hi Phil--

The flat looks nice and symmetrical, so the optics are nicely aligned. There seems to a be a lot of dust down at the 0.5% level. The obvious test is to see how well it corrects an image of a sky without gradients, perhaps at the zenith. I've found that it's hard to get a flat to correct so the sky shows no gradient. I often see a smooth 1% difference top to  bottom. I'd like to know where that comes from. At that low level, it's easy to correct it aesthertically, but you don't know that is correct.
However, since we're doing photometry, maybe the best test of all would be to shoot a series of images in which a star (or stars) is moved to a raster of locations in the field, say 7 wide by 5 high, and then see whether the magnitude is constant at all locations, especially the corners. Time consuming but it would test everything about your technique. 
PS: JPEG.of the master flat below.


bkl's picture
Light Box Solutions

Hi Ed,

I must have tried every solution under the sun (and not under the sun!) to get good flats. Besides sky flats, I have resorted to flat panels illuminated by tungsten (or other suitable blackbody radiator) bulbs on a dimmer. The panel has to be painted with a paint that appears "white" from IR to UV, basically through all the ranges you intend to image. But you knew all that. Here's the paint recipe.... and the original source:

Recipe for the high reflectance white paint, as taken from the paper by Wu et al. (1972, AAS Photobulletin 1, 9).

In practice it seems best to mix this paint just before use. A coating of Krylon 1502 flat white paint was sprayed as a primer.

To make one pint:

 1.     Heat 50ml of distilled water to 52-66 C (125-150 F) and slowly add 2.25 grams of elvanol polyvinyl alcohol (Grade 72-60), mixing until all the alcohol dissolves.

2.     To this mixture add 150 ml of distilled water and 200 ml of 200 proof anhydrous ethyl alcohol.

3.     Then slowly add (stirring continuously) 227 grams of USP grade barium sulfate to the mixture.

Use it all. The Barium is exactly easy to dispose of. I just finished making a 1m square panel for the new scope here, and it's working well. I know this is not a box solution... which is rather nice, but this enables flats in the middle of the day or night in a closed building. 

All the best,

~john (BKL)

Richard Berry
Richard Berry's picture
How do we start a new thread on "Making Good Flats"?

How do we start a new thread on "Making Good Flats"?
Making good flats is basic, a combination of equipment, software, and technique. I think it would be good to summarize the magic in a two-page "Best Practices" post in the Section. I uploaded the files to create the page to Sara, so it should be up after the Memorial Day weekend,

BSJ's picture
Starting a new thread

Whenever someone has a new topic to discuss, they should start a new thread. To do this, go back to the main forum page: and click "New Topic" just above the topic list.

More general information on forums can be found in the blue box on the main forum page or here:

Many thanks. I'm sure that this is going to be a very active forum with lots of useful discussion.


Calculad's picture

I guess I should have done that. Sorry


STHO's picture
Thank you Richard Berry


Thank you for coordinating this group.

I have had a lot of experience building and automating astronomical observatories and equipment and this is a welcomed section.

Again, thank you and the AAVSO for this effort.

Thomas C. Smith

Dark Ridge Observatory

Richard Berry
Richard Berry's picture
Hi Tom--

Hi Tom--
Thanks for posting. Please subscribe to the Section. That way you'll receive an email notice of new posts. Good stuff is coming down the line with the Observing Sections. This summer we'll be doing an Observing Section Fair....
Meanwhile...You probably have some great finished projects you could write up. I'm going to do a couple (in fishing they call it "chumming," basically throwing fish guts in the water to get the fish biting).
I also see that a short, comprehive, and authoritative "Best Practices" post about photometric filters is in order. I figure it should be less than 1000 words. I am not sure how to work this: if someone who really knows filters types it up and sends it to me as a docx, I will format it and we'll post a link in the "Best Practise" blue box.

TRE's picture
Thanks Richard

Looking for some good best parctices, some great ideas, some experience from practiced technicians. I have to admit that I have shunned the automation project to spend more time taking data. But if you experts can motivate, who knows.

The other half of the equation seems to be absent so far. We seem to have folks that know how, but no one actually asking how.

So I'll kick it off with a question: For portable equipment with no autoguiding, is it vital to level the mount? I know folks that don't level the mount but they autoguide.

Hope the questions get into the details.



Bikeman's picture
Maybe we'll want to open new

Maybe we'll want to open new topics for questions like this in the future, but anyway, here are my 2 cents on the question:

Q: Do I need to level an equatorial mount?

A: No. But then again.... to some degree,  It depends..

The (only) important part is to align the RA axis of the mount to Earth's axis of rotation, and if you've done that, you are fine. Period. No leveling of any part of the mount needed as long as this alignment is ok.

Problem is: How do you do the polar alignment? If you do that by using e.g. Polaris as a reference in the northern hemisphere by using a polar alignment scope built into the RA axis, that process will require leveling at some point to use the reticule built into those telescopes in the right way. This is because  you need to convert the local siderial time wrt the culmination time of Polaris to do the fine adjustment as Polaris is not exactly at the northern celestial pole. But the scales etched into the reticule depend on a level mount, or for some Skywatcher scopes, you need to put the counterweight rail level and then put Polaris into a position that the Synscan hand controller (or an app for your smart phone) will tell you. 

But there are other, "photographic" methods, not using such a polar alignment telescope, that work with calculated corrections to the alignment based on how stars move across your sensor when you move the scope  (e.g. SharpCap's polar Alignment assistant feature described here ) And for that, you really don't need any leveling.  






Richard Berry
Richard Berry's picture
Leveling the mount?

Hi Ray--

As the previous answer made clear, there's no need to level the mount. Just make sure the polar axis rotation is aligned with the celestial pole. A great deal has been written about polar alignment, but IMHO, the QHY PoleMaster is fast, efficient, and accurate.
There are several features of the PoleMaster method that are not immediately obvious. The device can be put anyplace on the mount. You can even use blue tape to hold it. just make sure it cannot wiggle. This means you can align fork mounts by attaching it to the end of a fork arm pointing at the pole. You attach it to the telescope so long as you do not move the scope in decliation once you begin the alignment procedure. The only constraint is that the pole must be in the field of view. 

If you leave the PoleMaster attached to a remotely operated telescope, you can verfiy the accuracy of the polar alignment in the event that tracking appears to have mysteriously degraded. If you're portable but not autoguiding, really good polar alignment will often allow you to make exposures a few minutes long. That can works nicely for time-series photometry.


Calculad's picture
Scope Buying advice


I'm new to the AAVSO although not to photometry, having just uploaded my life's observations to the database. I hope I am in the correct place for pretty general buying advice. I had been observing for many years with an SSP3 photometer and an 8" Newtonian reflector but was hoping to buy a Schmidt-Cass as I may need a portable instrument on some occasions. I guess I have a few overarching questons to kick-off with.

1.What is practically the largest portable model?

2. To an inexperienced Sch-Cass newbie the market seems to be dominated by Celestron and Meade. Is there much between them in regard to photometry, bearing in mind that we need a reasonable light bucket and don't demand ultra perfect optics? (I may be wrong on this assumption)

3. Are there any particular problems buying 2nd hand with these?

4. Is an altazimuth mount suitable for photometry? My old Newtonian was equatorially mounted.

5. I'm sure there may be other things like dewing and wind I need to consider so general tips would be very welcome.


Richard Berry
Richard Berry's picture
Scope Buying advice

Hello "Calculad"--

Since you've been observing and doing photometry, you already know the basics. 

The largest portable telescope depends on your size and strength. Most people would agree that an 8-inch SCT is portable, and a 10- or 11-inch is startting to push the limits. A 12- to 14-inch to more than most people can handle, but okay for two people.

Super-duper good optics are not necessary, but your do not want poor optics. If you buy second hand, make sure you star-test, or view planetary images. Poor optics in an 8-inch won't give a good view of Jupiter, and any decent optics will. 

I think you'll want a good-quality equatial mount if you plan to use the SSP3, because  you want to be able to place the star in the diaphragm and have it stay there. The alt-azimuth mounts I have seen in operation are okay for visual observing, but the tracking motion can be a bit jerky. The new mounts may be batter than those I have seen (others may wish to chime in).

Unless you observe from a dry location, you need a dew sheild and possibly heater tape to keep the corrector plate dry. I live in Oregon, and both are needed about 80% of the time. The aluminum dew sheilds are best because they fit on snugly and will not droop into the light path.

If there is any way you can set up an observing shelter or observatory, do so. Having a fixed location with power and shelter from lights and wind makes a huge difference.

What makes you want to change from the current Newtonian? Weight? Bulkiness? Tracking? What did you like about it, and what did you find problematic?


Calculad's picture
Reply to Buying advice

Hello Richard,

Thanks for taking the time to reply and for your advice and questions which made me think about what I want.

 I have had an enforced break from observing and have also moved house. Previously I had a run-off roof type observatory in a town location. The set-up worked well apart from house lights, breezy nights and rather bright sky which limited me to about 6.5mag for photometry. Once polar aligned I had no trouble tracking and keeping stars in the ring.

My programme stars were bright circumpolar variables of no particular type, and with a good clear north sky was able to follow them continuously (ish).

As I plan a return to observing, my reasons for a change are that I am now a bit hemmed in (but sheltered) by trees and would have liked the option to do photometry, but also for more informal observing over a bigger sky with family, neighbours etc. I do have a much better, darker sky. Hence the portability option, but equatorial mount sounds safer.

My house on the Isle of Wight, UK is essentially at sea level and would certainly suffer from dewing.

Perhaps my efforts would be better channelled in the direction of an observatory first.

I may have the option on a very nice 14" Meade and SX CCD soon, which would certainly need one.

I have no experience of CCD’s though and would probably stick with the Optec

Thanks again



Bernhard's picture


1) As said, the weight you can handle. Maybe try out different weights at a sports center or a telescope shop (-;

2) I think photometry is stable to almost every telescope. I us a 20 year old Newtonian and a used 4" achromat skywatcher.

3) Find a re seller, which can tell you honestly why he is selling. No more time.. bigger scope... To find out if there are problems with focusing, cameras, just ask for a test night...

4) maybe someone here in the forum has experience with ALT AZ?

5) General tips

a) Usability: Mhhh ok, I have a AZ EQ6 which can handle ~ 20kg. So my dream is a 12" telescope. The poor side is... it needs to be an expensive carbon tube or an also expensive EQ8 or similar..  But with this weigth.. the telescope should be stationary in a backyard or wount set this up every night.

My AZ EQ6 is stationary as it is, so i need ~15 min from powering up to taking photometry.

One possible problem with SC's are the big focal length for variables. You already know that the FOV would be so small, that one do not have proper compare stars..?? Celestron has an expensive but good reducer kit.. what was the name...??? hhmmm... RASA?

Now at my balcony & the 8 inch Newtonian, i found out, that this setup is already the biggest for this place. I live in a big town with a bortle  6 - 8 sky. So a bigger scope, maybe with an observatory dome... would be appropriate in a hause with a garden or backyard...for a permanent setup.

b) Projects: ask yourself, which projects you urgently want to do, which are not possible with your actual setup (e.g. exoplanets needs more focal length for the resolution of mmag  ofthe transits... -> barlow lenses..)

regards wbea

Calculad's picture
Scope buying advice

Hello Bernhard (wbea),

Many thanks for your considered reply to my post.

Some points and reasons for a change have been commented on in my reply to Richard so I won’t repeat them.

Regarding the focal length, with Optec SSP3 photometry I move the scope between variable, comparison and check stars and offsets to sky, so I don’t think that a long focal length should be a problem unless I have misunderstood your point. Maybe CCD observer’s have to worry about this. Please come back to me on this if I am wrong.

I would almost certainly be buying second-hand or maybe even reviving my old scope following your and Richard’s advice.

Thanks again,


Bernhard's picture
Hi Kevin,

Hi Kevin,

ah so you are a 2 nd generation var star observer ( if you allow this classification (-; )

1st generation: eyes ,eyes through telescope and binoculars

2nd gen: using electronic photometric equipememt, through a telescope, varying between, var, comp, check stars..

3rd gen : using ccd or dslr, where one photo has the var, comp and check star

4 th gen: Data Mining without a telescope, only with computer...


I was refering to the 3 rd gen obs., where one photo has to cover all stars. (-: therefore with the shorter the focallength, the more FOV of the picture has more good compare stars.


regards bernhard

TRE's picture
my experience

1. Size, I had an 8" Az-EL Meade with the tripod. when I moved it, I was glad it was not larger.

2. No difference in manufacture as long as optics are reasonably colimated.

3. I have had good experience with 2nd hand. I used Astromart or personal contacts.

4. I used short exposures, <60 seconds, with an Az-El Meade for time series photometry. AIP4WIN was able to follow the stars despite rotation. VPHOT would likely follow the rotaion, but I have always used an equatorial for VPHOT.  No experience stacking rotated images, but I suppose it can be done.

5. Use a dewsheild. It also helps minimize light pollutions from the side.


Calculad's picture

Thanks for your comments Ray


Bernhard's picture
Dylan O'Donnell

Dylan O'Donnell

has several good reviews about the RASA F2 you may want to look.


@Kevin: Maybe Celestron Faststar or Hyperstar is interesting for you.

Richard Berry
Richard Berry's picture
RASA 11 inch f.2.2

Hi Dylan--

The 11-inch RASA is my primary imaging telescope. This link is full of info about the RASA:

Traditionally a "White Paper" is an information document published, for example, by a chip maker, containing all the technical details about a new product for EEs who might use the chip in a device they are designing. In this case, the document explains why the RASA has no eyepiece and why the camera sits up front on the corrector plate. It includes ray traced spot diagrams and other tech details.

The difference between the Fastar and Hyperstar and the RASA is the former are after-market products added to the standard f/10 telescope, while the RASA is designed from the ground up to be an imaging camera. It covers a wider field of view, and images are probably better (but I have not compared them). 


RASA 11 inch f.2.2

Hello! Just curious which camera you use with the 11" RASA. Best regards.


Richard Berry
Richard Berry's picture
Currently using an Atik

Currently using an Atik Horizon camera, sometimes with Infinity software (real time stacking) and other times with Artemis (for photometry). I have used a QSI 532, a Canon 60Da, and an Atik Infinity in the past. The RASA works well with all of them.

I like the 1.6 x 1.2-degree field with the Horizon. It's a CMOS camera with variable gain. By setting to gain to high, I;ve done high-cadence photometry -- 10 second exposures -- on faint stars. 



MMU's picture
RASA and filters?


What are your options for using photometric filters with the RASA? Are you using the monochrome version of the Atik Horizon?

- Mark

Richard Berry
Richard Berry's picture
Hi Mark--

Hi Mark--

It would be difficult to use the RASA for photometry with filters. The spacing betwwn the mounting ring and focal surface is fixed, and the light cone is large and steeply converging. Using a single filter such as V would be easy. I suppose one vould make a special adaptor with holder for slip-in filters, but I have not done so. 

I have the Bayer version.of the Horizon camera. Out oif curiosity, and knowingly breaking all the rules, I've taken some time-series images and extracted TR, TG, TB light curves. Basically, iit's the aame as doing photomerty with a DSLR. I have also tried an 8-hour binned time series on V405 Aur with the camera binned 2x2 and the gain set high, at a cadence of six images per minute. Each binned pixel had one Bayer element. Several cloud bands crossed during the night. The 4-minute modulation of the white dwarf is noisy but clearly visible in the light curve. I have not had time since then to examine the dataset carefully.




dleemoon's picture
RASA 11"

The is a you tube video which shows a filter holder fir the RASA 11" telescope:

StarLink satellites

Hi Richard,

Elizabeth suggested that I contact you regarding the email I sent to AAVSO which follows.  I thought this possibility for contributing may be of interest to our members.

Best wishes,


Subject: Re: Fwd: [Website feedback] Possible project for observers

From: Elizabeth Waagen <

Date: 7/22/20, 10:16 AM

To: Thomas Barnes <


Hi Tom,

Thank you for your email expressing your concern about the StarLink satellites and sharing the outcome of the SATCON1 Workshop.

We have a new online discussion forum on Instrumentation and Equipment ( It is managed by Richard Berry. I recommend that you contact him as to whether or not it would be appropriate to post your message there.

You can reach Richard through his web contact link in the first thread in the forum (the sticky called Welcome to the New Section). His name is in blue above his photo - click on that and then on the Contact tab on the page that comes up.

When I saw your email I checked your record in our people database to make sure we had your current email address. I saw that you joined the AAVSO in October 1979 (2 months after I started working at HQ with Janet). We have both been AAVSOers for a long time! Thank you so much for your dedicated support all these years - we are very grateful to you.

Take care, and best wishes,



Elizabeth O. Waagen

From: <

Date: Tue, Jul 21, 2020 at 3:42 PM

Subject: [Website feedback] Possible project for observers

To: <

tgbarnes ( sent a message using the contact form at

In the most recent Currents (#68) from NOIRLabs there is a project associated with gathering data on the StarLink satellite impact. It's listed under Results of the SATCON1 Workshop: "The group finds that there are immediate and long-term needs for broad, coordinated efforts between researchers, observers, astrophotographers, and amateur astronomers to conduct observations of satellite constellations and interpret the data."  Some of our members may be interested in participating.

Best wishes,


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