Skip to main content

Right Equipment?

GWOOD
GWOOD's picture
Offline
Joined: 2010-10-10

Just got my notification from Astro-Physics Co. that I can now order an AP1600 GTO mount. I only have a few days to go or no-go.

My interest is to 1) get Go To capability to speed up target variable star locating, 2) push my visual limiting magnitude down to +14/+15 range to follow stars down to minimum magnitude (currently using an LX200-8" vintage 1986 - no Go To capability generally limited to about +11/+12 visual magnitude on the best of nights her in NC), and 3) prepare for future move to CCD photometry. 

The AP1600 will definietly be a great mount to have with or without the absolute encoders. Other mount option considered is a Software Bisque MX -- big difference in load capacity and price ($$). Looking at either a Celestron Edge 14" or a Deep Sky Instruments 14-1/4" with the ceramic mirror option -- again a big price / performance difference.  I plan on starting out with visual and then adding CCD capability in the future.

Do I go for the best most expensive option or save many thousands of dollars and go with the lower cost option? Will one option or the other be a better long term (20 + years) performance, reliability choice? Other options I should consider? I amn not interested in Dobsonians.

 

Gary Wood

How much of a do-it-yourself person are you?
KTC
KTC's picture
Offline
Joined: 2010-12-08

How much of a do-it-yourself person are you?

If you DIY well...you can pick up used gear....tweak it so that it works well...and save $$$.

The AAVSONet scopes here at Astrokolkhoz are not high end rigs.  They do pretty good photometry, did not cost too much, and the savings allowed me to set up multiple scopes...instead of only one, high-quality rig.

Right Equipment
MDAV
MDAV's picture
Offline
Joined: 2010-07-23

Gary:

I would like to give some of my recent experience. Do not underestimate the expense or the time and effort spent on the learning curve- especially if like me you only get a few days per month to spend on it.

Back in May I was given a 12"classic goto LX-200. I took the scope with the intent of learning to do photometry.  While I like the scope and the tracking and goto capability it has been an expensive learning curve. First it is very heavy- which means that not being  permanently mounted (pointless in Morro Bay,CA.) it will not be used that much.Second-it is not that well built mechanically. My older laptop wasn't up to the demands and having replaced it and obtaining a Canon 600D DSLR as well I am out a couple of thousand bucks. On top of that I have had to spend another six hundred on a Meade  equatorial wedge- which is a very mediocre mount given the asking price. I have had to spend far more time than I should have making modifications to it. I have not yet put out the money for a guiding scope and autoguiding camera. Then there was the time learning how to use the camera and getting the appropriate cables and batteries to use in the field. Then there is learning the software (IRIS and Starry Night ) and how to take and process flats, darks, lights etc.  I was stunned by how poor my initial photometric measurements were (exceeded the scatter of my visual estimates made at the same time) . While my work has greatly improved I still do not consider my results consistent or good enough to start submitting photometric data yet. 

The net result though is that my submissions of estimates has been reduced by 90 percent since I obtained my computerized "free" telescope.  

I would recommend you get somone  who already does this to mentor you. I cannot overemphasize this. I have probably made every mistake it is possible to make. If I hadn't been an amateur already for thirty years I would simply have given up on photometry. A mentor would have recognized I was trying to do too much too quickly.

Having said that a lot of this has been fun. I have learned a tremendous amount about the camera and telescope. I smile now at my naivette of only a few months ago. I have some really neat looking images I took myself. and have spent hours on hours perusing them looking for variables. The number of star images on some of them is truly amazing- far more than I had thought. In fact that has been part of my problem- making an annulus that doesn't include a star in the outer ring.

 

 

 

 

photometry
clittlefield
clittlefield's picture
Offline
Joined: 2010-07-27

Hi Gary,

I have a couple of brief thoughts about your situation. First, the AP mounts are famous for their ability to track past the meridian. This is a critical feature for time-series photometry, and many German equatorial mounts are incapable of tracking past the meridian for very long. Bruce Gary, an accomplished CCD observer, has a webpage (http://brucegary.net/CGE/x.htm) which highlights some of the problems with this limitation. If the AP 1600 is able to track as far past the meridian as its predecessors, then this isn't as much of an issue.

Second, David points out that learning the software can be a pain. When you're getting started with photometry, my advice would be to download the free, 30-day trial version of MaxIm DL. The photometry tool in MaxIm DL isn't perfect, but it offers a very intuitive user interface. It's much easier to use than IRIS. Although MaxIm DL can get pretty expensive, the trial version would let you get your feet wet with doing photometry and outputting your data in AAVSO format. Once you've tried that a few times, the learning curve for free software like IRIS wouldn't be so bad. (Or you might decide to purchase a program like MaxIm DL or one of its competitors.)

By the way, if you'd like a CCD mentor once you get your camera, as David suggests, I'd be happy to help you. I had two mentors (one an amateur and the other a professional), and they made CCD observing a lot easier. CCD photometry is a lot of fun, and it becomes second nature after a while.

Best Regards,

Colin (LCO)

Right technique may be critical
KTC
KTC's picture
Offline
Joined: 2010-12-08

...I was given a 12"classic goto LX-200. ...it is very heavy

One advantage of German mounts...the entire rig ususally comes apart into several components (and the OTA is easily removed)...considerably reducing weight of the heaviest component.

not being  permanently mounted (pointless in Morro Bay,CA.

Foggy coastal weather?  Often humid?

I used to live only a couple miles from the center of a city, population 2-3 million...bad light pollution.  (And other problems...frequent blackouts/brownouts, and during autumn locals would burn leaves....producing a steady 'rain' of leaf ash some nights)...but my scope was permanently mounted in the front yard (unshielded streetlight 20 yards away, 12 foot security walls blocking much of the sky)...and on clear nights I was set up and taking data in 20 minutes.

Permanent setups can be good....even with all the local/site problems.

I have had to spend another six hundred on a Meade  equatorial wedge- which is a very mediocre mount given the asking price.

Don't pay the asking price.  Get a used one.  Or, find a friend that can do some metal fabrication.  I have welded up more than one wedge....using junkyard/scrap steel that cost zero.  My welder cost less than what you paid for your one wedge.

I have not yet put out the money for a guiding scope and autoguiding camera.

Before you try autoguiding, I recommend you evaluate your scope for declination drive backlash (not good, but tolerable), and stiction/weird reversal (bad...must be fixed, or a workaround must be implemented).  Many Meade's suffer from stiction/weird reversal.  But often this can be fixed.

Then there is learning the software (IRIS and Starry Night ) and how to take and process flats, darks, lights etc.

What automation software can talk to Starry Night?  (My long term goal is getting a scope that can run unattended through the night while I get proper sleep.)

...that has been part of my problem- making an annulus that doesn't include a star in the outer ring.

Why are you striving for this goal?  Most photometry software I know of use algorithms (such as mean of the median half) that will reject several stars in the sky annulus.  That works well unless you are shooting in very crowded Milky Way fields.  (Posting some sample images would be very helpful to see how 'tough' your photometry situation is.)

Meridian flip and Maxim photometry software
KTC
KTC's picture
Offline
Joined: 2010-12-08

AP mounts are famous for their ability to track past the meridian.

Years ago, when researching mounts/capabilities for CCD photometry rigs...I discussed this point with someone with much experience with various mounts...German, fork, high-end, low-end, etc.  He mentioned that AP mount owners would sometimes boast of their mount's past-meridian tracking performance.

But then Old Man Murphy would strike.  Human error for mount flip settings?  Human error on mount command at 3AM?  Mount driver buggy?  Mount firmware goes dumb?.....no matter....

CRASH!

Those same previously-loudly-bragging AP mount owners would repair the damage...and reset their mount flip/travel parameters to much more conservative values...such as flipping at the meridian.

I have three German mounts here.  They all have to flip at the meridian.  They all do pretty well for photometry.

What will you do with an AP mount when you must track six, seven, or more hours past the meridian for a long time series?  Can you avoid flipping entirely?... or do you flip three hours past the meridian?  If you do much long-time-series photometry, you may find that flipping at the meridian is just as effective as flipping the mount at the very, extreme last moment of mount travel past the meridian.

Evaluate your scope for flat field accuracy.  Don't just look at a flat-calibrated image to see if it appears flat....make photometric measurements to prove it.  Problems with scattered light?  Find the problems and fix them.

The photometry tool in MaxIm DL isn't perfect, but it offers a very intuitive user interface.

Maxim uses an unnecessary 'artificial star' in (some? all?) its photometry routines.  I've heard Arne call that 'kludgy'.  It's an extra step in the process...and extra steps mean more opportunities for things to go wrong.

There are many photometry packages out there.  Some free, some inexpensive, some expensive.

Don't forget VPHOT.

Good luck, and keep the questions coming.

Meridian flip and Maxim photometry software
GWOOD
GWOOD's picture
Offline
Joined: 2010-10-10

Thanks for the commenst.

VPHOT is a great AAVSO member benefit. I know one local university professor who uses MIRA AL instead of the old IRIS software. MaxIm DL is in the same price range as the MIRA series software, depends on if you want just photometry routines or telscope control + PR.

Tracking 3-4 hours west of the meridan would be about my limit based on trees and sky conditions at my site. Considering the high end equipment I am looking at "portability" might be "transportable" to a dark sky site in Virgina, Georgia, Penn. or out west for a few days once or twice a year; but I figure a permanent setup (observatory) is more practical and would be used much more frequently.

Perhaps I should just drop down to an AP 900 or a used AP 1200 (if I can find one), and a Plane-Wave 12.5" CDK and save about $10K. I could just buy a Celestron 14" Edge/CGE PRO with f/6 focal reducer, hope I get a good unit, upgrade the cables upon arrival, and see how things go. In this case I am down to about $10K total expenditure.

A camera for any of the setups -- I need suggestions. I am not ready to spend $20K on an high end Apogee. How about a QSI 685 series with filter wheel/Astrodon filters and OAG? Right or wrong match for any of these scopes?

Save even more money
KTC
KTC's picture
Offline
Joined: 2010-12-08

Perhaps I should just drop down to an AP 900 or a used AP 1200 (if I can find one)

I have built three forks here...sized to carry a C-14 or similar...and forks long enough so that I can point at +90 dec with no problems.

Parts cost?  About $3,000.

I don't have a mill, lathe, or any precision machine tools.  I just have a saw that can use an abrasive cutting wheel, and a small drill press (table top, not floor standing)...and a stick (SMAW) welder.

If you want, I can send photos/ideas.

...and a Plane-Wave 12.5" CDK

All the C-14's here are pre-Edge HD...and can often be found for about $2,800.   Add a focal reducer...they produce decent photometry data.  I leave the more expensive Edge HD OTA's to the purty piskher takers that want tack sharp stars corner to corner.

How about a QSI 685 series with filter wheel/Astrodon filters and OAG?

Find a used ST-8 and filter wheel.

Add a high-resolution encoder to the RA axis of the home-made fork....eliminate drive periodic error, and never autoguide again.  Ever.  This means you never have to depend on guide stars.  Scoff at passing clouds.  Take lots of data.

Right Equipment
jji
jji's picture
Offline
Joined: 2010-07-24

Well this thread did it.  It got me to subscribe to whatever forum this is...at least temporarily.:)

AP makes quality mounts.  Thier customer service is outstanding and The owner of the company and all of the staff seem to check the user's group daily and participate frequently.  That in it's self is worth something.

I have had a C14 on a AP1200 for almost a year now.  I am very happy with it and my productivity has gone up.  I can make unguided 120 second exposures with an 0.87 pixel scale all night long with never a reject.  The AP1200 is probably an over kill for a C14.  In fact weight wise I could mount two C14's and a Losmandy mount on the AP1200.  But I enjoy the extra capacity.  The 1600 will really be over kill for a C14.  But on the other hand, you will be able to upgrade to pretty much any tube you want to in the future with out concern.

Only you know how certain you are to upgrade to CCD imaging.The 1600 will be way more than is needed for visual observing.  The AP900 or even the Mach1 would probably handle the C14 visually just fine.  In any event I wouldn't spend the extra bucks for the precision encoders until you try the mount.  They would be no help at all for a visual observer and probably not needed for 99% of CCD observers.  I *think* you could probably add them later.  They are expensive.

One thought, since the AP1600 is the replacement for the AP1200, and some folks just have to have the newest and the greatest, there will probably be some AP1200's for sale in 6 months or a year.

AP mounts track past the Meridian by spoofing the clock in the hardware controller.  Automation programs like ACP don't like that.  So I'm not sure how much this option is really worth.  Most German mounts don't track past the meridian and everyone gets along just fine.

AP mounts generally don't go "crash" ;)  I've heard the sad tale of several users now who have tracked their cameras into their piers and there just isn't enough torque in current limited motors to do much damage.  I've slewed my mount (in a meridian flip gone bad) until it was brought up short by the cords without damage.  I beleive that the Bisque mounts also have some sort of shut down provision when the motor's stall.

You don't need the artificial star to do routing photometry with MaxIm.  I've been using it for severeal years and find it adequate.  In any event, take advantage of the free trial before writing the check.  You will probably need MaxIm if you automate anyway.

As far as portability is concerned, I wouldn't want to use my 1200 as a portable mount.  It is a handful.  If you are 20 years old and a body builder, it won't be a problem.  AP mounts break down into two major components, the RA assembly and the Dec assembly but they are a hand full.  And a C14 is a bigger handful than the mount.

Good luck.  and remember that "wives and telescopes come and go but mounts are forever".  Of course I am on my 1st wife and my 4th mount.

Jim Jones

 

There is a better way :)
lmk
lmk's picture
Online
Joined: 2010-07-23

Golllllllllyyyyy, After suffering through to the end of this thread, all I can say is why not try visual photometry with a big Dob and Ethos eyepieces? You'll save 99% of this torture, enjoy your free time again, and still contribute 0.05-0.1 mag accuracy to the AID...Lol.

Mike LMK

CCD observing isn't as hard as it might seem
clittlefield
clittlefield's picture
Offline
Joined: 2010-07-27

As I look over this thread, I realize that it must make CCD photometry seem hopelessly complicated, as Mike points out. Once you get past the initial expense, it really isn't that difficult, especially with all of the online help that's available to new CCD observers. As I mentioned in my earlier post, CCD observing really does become second nature; the learning curve today isn't as steep as it once was. Actually, I've found observing with a CCD to be quite enjoyable and rewarding.

I think that this thread is emphasizing that there's a lot of room for individual preference with CCD observing -- and not that it's overly difficult per se.


Colin (LCO)

Quality equipment+software=Photometry zzzZZZzzz!
FJQ
FJQ's picture
Offline
Joined: 2010-07-25

I've been using a AP1200 mount and 13" cassegrain with CCD autopilot/Maxim/Sky6 for automated photometry acquisition for the last 4 years.  Your choice of a high end mount like an AP1600 is great for automated CCD image taking.  I usually shoot 12 different target a night in B & V filters and let CCDap shot the twilight flats and dawn darks/biases.  My problem isn't getting the data per se, but finding the time the go back and go through the gigabytes of images to reduce.

One thing I dont like about catadioptric cassegrains are the "dew-collecting" corrector plate.  If your humidity goes over 35% during the night, you will get dewed-out with these types of scopes; I know peps will say, "just get a kendrics,"  but the idea of "hot" corrector plate to acquire data thru doesnt sit well with me.  The Planewave 12.5" to me is a more resilient instrument if you want to do all-night photometry.  Once you have your automated photometry system going, you'll never look back to the bad old days "nursing the telescope" to get decent CCD data.

James Foster

Los Angeles, CA

http://www.astroimage.info/images/equipment/obs2.html

Dew heaters - even in New Mexico
KTC
KTC's picture
Offline
Joined: 2010-12-08

One thing I dont like about catadioptric cassegrains are the "dew-collecting" corrector plate.  If your humidity goes over 35% during the night, you will get dewed-out with these types of scopes; I know peps will say, "just get a kendrics,"  but the idea of "hot" corrector plate to acquire data thru doesnt sit well with me.

I have dew heaters on all rigs here in New Mexico.

On the C14's I use 25 - 35 watts of heat for the corrector plate/dell/dew shield...all the time.  C11's get about 15 watts.

In Sept/Oct...monsoon is ending, but it's still humid.  (And 'backdoor' cold fronts from the northeast in Nov, Dec, Jan are often humid events.)  If it's 45F air temp and 70% relative humidity...I can keep operating all night long, but I'm close to abort critera.

How warm does such a corrector cell get when you heat it in such a manner?  Perhaps 10F above ambient?  I can't trust my fingers to tell me if the dew heater is getting power...I add a small indicator LED.

An interesting point - when it's 25F air temp, I can tolerate 80% relative humidity and keep running.  The morning will show a very thick frost - pretty to look at.

If you are going to push the humidity limit, and especially if you are agressive about CCD cooling...you probably need a small heater (1 watt is what I use) for your CCD window.  Now that I have them on most CCD's here...I never lose data because of a fogged window.  (But I used to suffer that problem on wet nights in the past.)
 

Why not use remote telescopes?
PKV
PKV's picture
Offline
Joined: 2010-07-26

Many amateurs invest $20,000 or more for a nice telescope, mount and CCD camera and later may not utilize them fully due to location, clear nights per year, lack of a permanent setup, the lack of commitment to reduce 10 or more images per year, etc.  $20,000 is a lot of money for an initial startup.  Another option would be to use AAVSONet or another remote telescope service like iTelescopes or Sierra Stars.  I use the Sierra Stars 24" and it costs $0.85 for a 30 second Johnson V exposure.  With a V filter I can get down to magnitude 15.5 +-0.04.  In unfiltered mode, I can get down to magnitude 17 to 18 +-0.1 with a 30 second exposure.  

If I do 10 exposures a night for 180 nights out of the year, my dollar outlay is $0.85 x 180 x 10 = $1,430 per year.  It would take 13.98 years at this rate to equal my initial $20,000 investment in equipment.  Using AAVSONet on the side would dramatically reduce one's expeditures.  However, I am a slave to the weather patterns at Sierra Stars Observatory in CA near Lake Tahoe.  I make my requests before 7 PM CDT the night before and my images are in VPHOT account at 10 AM CDT the next morning.  No mess with flats or darks, as my images are calibrated.  However, time series photometry would be cost prohibitive.  I too find about 10 images a night is my maximum given my available time for reducing images.

I do visual observing at home and remote CCD imaging using Sierra Stars 24" in CA and the Bradford RT in the Canary Islands.  I monitor Miras and some CV's with the Sierra Stars 24" and CV's in unfiltered mode with the BRT 14".  So, I enjoy the best of both worlds.  One needs to first decide upon an observing program, objects of interest, interval of object monitoring, desired estimate accuracy and available individual time to reduce CCD images.   Then one can proceed with confidence with the financial commitment for the required equipment.   Many observers enjoy making worthwhile CCD photometric contributions without large initial dollar outlays.  Other observers enjoy the convenience of having a fully equiped observatory available at their becon call.  Others just enjoy visual observing with minimal expense.  There is something available for everyone.

Kevin Paxson - PKV

And with the savings, one
wel
wel's picture
Offline
Joined: 2010-07-26

And with the savings, one could pay for the membership in the AAVSO!

GWOOD Request
KRS
KRS's picture
Offline
Joined: 2010-08-03

What are your sky conditions like?  This is an important factor as to the scope you choose.  I have light polluted skies, and my C14 can sometimes get to 14th mag.  With the mount you have described, I would suggest a C14.  There are time when an OTA is available for a reasonable cost on AstroMart.  I prefer that to ebay since AstroMart caters to astronomers and is more realistic in pricing.

Good luck to you in your search.

Roger

AAVSO 49 Bay State Rd. Cambridge, MA 02138 aavso@aavso.org 617-354-0484