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About CCD photometry

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struve's picture
About CCD photometry

Can I send my CCD observations if I don't use filters? Best regards, Juan-Luis

SXN's picture
Unfiltered Observations

You can submit unfiltered observations by specifying them as unfiltered when reporting. You need to report them as unfiltered using a V  (visual) zero point or R (red) zero point. [Comparing to stars with known V or R magnitudes]

Generally speaking unfiltered observations are most useful for stars where you re primarily concerned with a periodicity and not the absolute color or magnitude. Unfiltered observations of Miras are almost useless scientifically, whereas unfiltered observations of an eclipsing binary or superhumping CV may be more valuable.

AAVSO would prefer all observers submit filterd and transformed data, but we are not there yet in our training and education of our observers. Filtered and untransformed is acceptable. Unfiltered is okay for some specific stars, but you limit the science that can be done with that data.

struve's picture
Thank you very much Mike. I

Thank you very much Mike. I have some experience as an observer of Supernovae (I regularly send my measurements to Mr. David Bishop) and they are always CR (unfiltered by referencing the R-band in CMC14, a good photometric catalog). So, can I do the same with cataclysmic stars?

Precisely these are the stars more interesting for me. I would like to have a brief list (to start) of observations of some cataclysmic stars of the AAVSO CVNet. Can you help me on what are the most interesting?

I'm new to this.

Thank you very much again.

Best regards,

Juan-Luis (Spain), GCJ

rmu's picture
Very useful explanation

This is a very useful explanation from Mike, but I recommend you to get gradually accustomed to a photometrical filter Juan Luis ;)

Cheap CCD


I plan to by this cheap CCD for photometry:

Is it usefull? Have somebody used it?

In CCD Manual (page 10), there is that if it is possible, the CCD doesn't include antiblooming (AGB).

But in the datasheet of this CCD: Anti-blooming: Overload margin greater than 1000x.

What does it mean? Can I used it to photometry?


Thank you,


KTC's picture
Re: Cheap CCD

You can probably use it for photometry, but I recommend you test it for linearity.

I have no experience with this CCD, but I know it makes a good autoguider.

Because this CCD has antiblooming, that often means the rangeof linear behavior is smaller...perhaps only to 30,000ADU?  Your tests will answer that question best.

Perhaps the people at Starlight Xpress can tell you how to disable the antiblooming feature? (a jumper wire on a circuit board?)...or perhaps they can do it for you.

This is a small-chip CCD.  Your sky coverage/field of view will be rather small unless you use a short focal length system. 

This guider does not appear to be cooled.  That will make calibration a bit more challenging.

Good luck!

Cheap CCD


Dear Tom!


Thank you for your answer!


I have written to Starlight Xpress. I will see. If there is no way to remove anti-blooming, this CCD may be not the good for me.


I plan to use this camera with a 150/750 Newton. With this, the FOV is about 30'.




Thank you,



rmu's picture
Cheap CCD

Jat, all ccd's mounted in sx cameras are suitable for photometry, keeping in mind that linearity ends at some level that you can know testing the camera. With mi old mx-516 I learned it has a lineal response until 40000 counts by my own tests.

By my experience, a very good match for the 150/750 Newton is the ICX285AL, wich is mounted in the discontinued MX-916, but there is a mor modern equivalent model in catalogue. Unfortunately, this is more expensive than lodestar camera.

MJB's picture
script for autofocus in Maxim

Maxim allows one to set up a series of images in its autosave page.  However, it does not seem to offer a simple way to conduct an autofocus periodically during the sequence.  Does anyone have an autofocus script that could be inserted at the end of a slot on the autosave page to achieve this end?

KTC's picture
These links may help
roe's picture
autofocus routine

It is very easy to write a VBScript that will duplicate and enhance the autosave function in Maxim.  The "enhancements" might be more info in the FITS header (very useful if you use VPHOT).  The Maxim autofocus routine is also available to a script - but I haven't tried it yet.  If you are already using it in manual mode and know its idiosyncrasies, you should be able to run it from a script.

I can provide more info and sample scripts if you are interested.

SDB's picture
Maxim autofocus


Do you regularly use the Maxim autofocus routine?  I have never been able to get it to work successfully on mr RC-16.



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