16 replies to this topic

[emranismail11]

I am planning on starting up my own rig to run photometry, but I also want to eventually start doing astrophotography as well. My only thing with monochrome cameras is that the filters are gonna drain my pockets and I was considering getting a asi 2600mc or asi 533mc but will get the MM version of going with colored is virtually pointless. It will be on an 8'' sct

[hyiger]

What kind of mount do you have?

[jgraham]

I started using a monochrome camera and a Johnson V filter which worked very well. However, as color cameras improved I migrated over to color cameras for imaging and photometry and that what I have used ever since. The procedures are essentially the same, you just separate the RGB data and use the green data for photometry (you can also use the blue and red, but I never done that). You record the data as Tri-G. Works great!

[emranismail11]

What kind of mount do you have?

Dont have it yet but planning on getting an atlas eq g here soon.

[emranismail11]

I started using a monochrome camera and a Johnson V filter which worked very well. However, as color cameras improved I migrated over to color cameras for imaging and photometry and that what I have used ever since. The procedures are essentially the same, you just separate the RGB data and use the green data for photometry (you can also use the blue and red, but I never done that). You record the data as Tri-G. Work

Have you done exoplanet transits? Also what colored camera are you using? Has the data been basically the same or photometry or have you noticed "worse" data sets?

[GaryShaw]

Hi

Be aware that mono cameras and V&B filters are the baseline for photometry if you want the professionals to consider using your data. Having both V and B filters allows you to ‘transform’ your V and B photometric data to correspond with the standards established by the Johnson Cousins filters that, until recently, were available and have became the basis for serious photometry.

 

As mentioned above, it’s possible to jump through a few extra hoops and use a one shot color camera but it’s not serious photometry IMO and cannot not have the added value of being transformed. It you just want to get your feet wet with photometry, the OSC approach can suffice. If you want to contribute data that the professional community will more highly value, I’d suggest going with the generally-accepted approach using a mono camera and a photometric V filter. Once you confirm your interest and advance a bit, you could buy a B filter and learn to transform your data before reporting your observations to the AAVSO.

cheers

Gary

Edited by GaryShaw, 21 November 2024 - 12:21 PM.

[jgraham]

To be honest, I have been doing this so long that I have lost count how many different cameras that I have used for photometry, and each has worked well. It’s important to stay within the camera’s linear range (or be aware that you need to use a non-linear transfer function), which is pretty easy with modern cameras. Most seem to be linear for at least 90% of their range, and just to be safe I generally keep my target and calibration stars below 80% of full scale. As a sanity check I usually follow my stars for about a month and compare my results with data being submitted to the AAVSO whenever I start using a new camera. I have never had one fail me yet. And no, I have never tried observing an exoplanet transit, though I know some who have. If nothing else, it’s a great way to start. I highly recommend spending some time on the AAVSO website as there is a lot of excellent information on there. I also enjoyed David Levy’s book on observing variable stars.

 

Enjoy!

[River Hills]

I think that someone just starting to think about photometry should just use what they have to start with . Almost any rig can be used to do some photometry. One issue I personally had to face, and I still have not fully dealt with, is what do I want to accomplish. If the goal is to just do some eclipsing binary timings of brighter stars you will have a relatively easy time getting started. If the goal is to detect exoplanet transits, then greater demands on the equipment and technique is made. 

 

I am assuming that you are just starting out in the game ( you mentioned you want to start astrophotography soon) and with , literally, the whole universe beckoning, it is easy to see so many interesting things to do. In my own case, I wanted to do it all- lunar, planetary, solar, DSO, photometry, and so on. The thing I found is that no one setup can do it all at the highest levels, but most setups can do it all at some level. I found that my expectations needed to be examined as to what was achievable with my experience level, time available and budget. Unrealistic expectations caused me to be disappointed as I was not producing APOD images. After some time, and growing experience, I forced myself to examine these expectations. The point is that my expectations of what I wanted to achieve should drive what type of equipment I needed and the time I needed to devote to any particular aspect of the hobby. 

 

I think you have made a good choice of mount, the Atlas, as it is the foundational piece for anything you do. You have (or are getting) an 8" SCT. This is a popular choice as a very versatile scope. I have a C8 and have done lunar and planetary imaging and I think you will enjoy that. While I have done some DSO imaging, I have found that very challenging with my HEQ5 mount and such a narrow field of view. I have only started my photometry work but I found that the 8" and HEQ5 along with a monochrome 533 camera to be a very workable combination, but after some years of other types of imaging.  My initial results have been good, so I think you can do so as well. However, I have taken the AAVSO courses on Intro Photometry and using the AAVSO software, Vphot, and that was the time investment . In deciding that serious photometry is, at this moment, my main focus, my research led me to conclude that a mono camera and filters was where my budget could go. If I was just casually wanting to do photometry, and accepting that there are limitations, then a colour camera would be just fine. 

 

Whew, this getting longwinded. You did not ask a specific question, so the best I can offer about the type of imaging equipment to get is to get the camera that allows you to do what you specifically want to do, and then also accept that you just might need another camera down the road to meet different expectations. 

[Xilman]

Excellent photometry can be and is done with OSC cameras.  Just look in the AAVSO and BAA-VSS databases for many, many thousands of measurements made to date.

 

Quite a lot of valuable photometry doesn't even use filters at all, or if they are present as is inevitable in a colour camera, they are ignored. Time-series photometry is the obvious use case.

 

By far the most important contribution amateurs can make towards exoplanet studies is to time as precisely as possible the start, mid and end points of eclipses. It matters little how bright the star is, only that the dip can be measured.

 

Similarly, although filtered images are preferred, determining the rotation periods of asteroids from their light curves can be done perfectly well with unfiltered images. It is normal for an observer to run unfiltered where the at least two-fold light loss of a filter would give an unusably low SNR for a faint object which would be measurable unfiltered.

 

Much the same can be said for finding the times of maxima and minima of eclipsing variable stars.

 

I've used unfiltered images for both of the first two classes and will very likely start on the third once I know how to use the Seestar S50 reliably.

 

Advice: get started in photometry, learn your trade, and worry about filters later when you have a good enough case to invest the money.

 

Paul

[Xilman]

Hi

Be aware that mono cameras and V&B filters are the baseline for photometry if you want the professionals to consider using your data.

See my comments above about time series photometry and OSC measurements in the AAVSO and BAA-VSS databases.

 

They may be the baseline in some sense, but neither are essential for professional use of your data.

 

I've worked with professionals in large-scale projects and know of what I write. Another such project should start up this spring/summer, though, to be fair, I will be using a V filter on a CCD camera but only because that is what I already have.

 

In fact, many professionals are moving away from relatively broadband UVBRI photometry to using Sloane u'g'r'i'z' filters because their narrower bandwidths result in much smaller overlaps in transmission between neighbouring filters. I use r' often, especially for observations of asteroids, and i' on occasion.

 

Paul

[Ed Wiley]

I am planning on starting up my own rig to run photometry, but I also want to eventually start doing astrophotography as well. My only thing with monochrome cameras is that the filters are gonna drain my pockets and I was considering getting a asi 2600mc or asi 533mc but will get the MM version of going with colored is virtually pointless. It will be on an 8'' sct

If you are starting from scratch, that is, you have no camera, and your main interest is photometry.

If, also, you wish to do multifilter work, B, V Rc, Ic to the highest accuracy (contra precision).

Then you would like a monochrome camera, filter wheel and filters.

 

The downside is that if you also wish to do astrophotography you will have to have two filter sets.

 

That said, comments above tell you that OSC photometry in the green channel (at least) yields very consistent results with careful data reduction to untransformed Johnson V data. You do have to know about your chip as some have an IR leak and filter if needed. (Data in Blue and Red channels were rare in my not-so-extensive look at light curves.) Organizations like AAVSO and BAA-VSS know there are lots of amateurs with OSC cameras and they are eager to encourage them to get into photometry. Me too.

 

Since most of the data in the AAVSO data banks are, in fact, untransformed V. The OSC data comparable because the OSC green channel is very similar to the Johnson V "channel."  As I understand it, the professionals have ways of making these untransformed data compatible for their needs.

 

However, the fact remains: really high-quality data are data that have been transformed into the standard system* so that data from different photometrists are directly compatible with each other. For this you need at least two color "channels." This is easy with mono cameras and photometric filters. The accuracy in magnitude estimation using these photometric filters in amateur hands (CCD and CMOS) as been demonstrated using Landolt Standard stars (Wiley and Menzies, 2022, JAAVSO vol. 51, no. 1).  I have not seen a similar study using OSC Blue- and Green-channel photometry, but I would love to see such a study.

 

Ed

 

*Transforming to the standard system in differential photometry usually deals with color and instrumental magnitude response correction with the assumption that since target and comps are in the same air mass, no first-order extinction correction is needed.

Edited by Ed Wiley, 14 December 2024 - 01:35 PM.

[Xilman]

However, the fact remains: really high-quality data are data that have been transformed into the standard system* so that data from different photometrists are directly compatible with each other. For this you need at least two color "channels." This is easy with mono cameras and photometric filters. The accuracy in magnitude estimation using these photometric filters in amateur hands (CCD and CMOS) as been demonstrated using Landolt Standard stars (Wiley and Menzies, 2022, JAAVSO vol. 51, no. 1).  I have not seen a similar study using OSC Blue- and Green-channel photometry, but I would love to see such a study.

A very good point.

 

Now that low-cost OSC cameras are widespread and becoming more so (I'm thinking of DSLRs and smart telescopes like the Seestar) perhaps those two organizations should start such a study, using as wide a variety of OSCs as is reasonably possible. Needless to say, they should work together to avoid futile duplication of effort and to shorten the time taken to perform the study.

 

Should I make this suggestion to the BAA-VSS and you to AAVSO?

 

Paul

 

P.S. did you mean Blue- and Red-channel photometry? Green-channel is widely used as a V-substitute as you mentioned.

[Ed Wiley]

Paul,

 

You can read what Ken and I did. I think one of the reviewers said something like "I think we already knew this but someone needed to put it in print." One point: to do an accuracy study you really need to transform all the data as the standard stars are in the standard system. Of course, you can do a rough untransformed comparison. For example, my Johnson V coefficients are very small such that there is not that much difference between transformed and untransformed. B is another matter all together and since I must transform B, V comes along for the ride along with Rc and Ic. 

 

I think the DSLR manual speaks to transformation, but I never tried it. In fact, I found OSC photometry too fiddly for my taste. As I understand it, transformation is similar to photometric transformation, but I have never done it, so I might have the details wrong.

 

I think:...To transform TV to transformed TV (or whatever the designation is) you need transformation coefficients for TV and TB and you need images in TV and TG. This will transform both. If you want to do TR, then you need transformation coefficients for TV and TR and you transform both. No doubt some people know how to do this.

 

It is very simple with VPhot using photometric filters. Given that you have the transformation coefficients, you simply dump your (not uploaded) untransformed AAVSO observation files for all filters into TransformApplier (TA) and hit the button.(The transformation coefficients are stored in the telescope file and are unique for that scope.) Then upload the resulting output file through WebOps. I have no idea if TA works with OSC camera data.

 

Ed

[emranismail11]

I think that someone just starting to think about photometry should just use what they have to start with . Almost any rig can be used to do some photometry. One issue I personally had to face, and I still have not fully dealt with, is what do I want to accomplish. If the goal is to just do some eclipsing binary timings of brighter stars you will have a relatively easy time getting started. If the goal is to detect exoplanet transits, then greater demands on the equipment and technique is made.

I am assuming that you are just starting out in the game ( you mentioned you want to start astrophotography soon) and with , literally, the whole universe beckoning, it is easy to see so many interesting things to do. In my own case, I wanted to do it all- lunar, planetary, solar, DSO, photometry, and so on. The thing I found is that no one setup can do it all at the highest levels, but most setups can do it all at some level. I found that my expectations needed to be examined as to what was achievable with my experience level, time available and budget. Unrealistic expectations caused me to be disappointed as I was not producing APOD images. After some time, and growing experience, I forced myself to examine these expectations. The point is that my expectations of what I wanted to achieve should drive what type of equipment I needed and the time I needed to devote to any particular aspect of the hobby.

I think you have made a good choice of mount, the Atlas, as it is the foundational piece for anything you do. You have (or are getting) an 8" SCT. This is a popular choice as a very versatile scope. I have a C8 and have done lunar and planetary imaging and I think you will enjoy that. While I have done some DSO imaging, I have found that very challenging with my HEQ5 mount and such a narrow field of view. I have only started my photometry work but I found that the 8" and HEQ5 along with a monochrome 533 camera to be a very workable combination, but after some years of other types of imaging. My initial results have been good, so I think you can do so as well. However, I have taken the AAVSO courses on Intro Photometry and using the AAVSO software, Vphot, and that was the time investment . In deciding that serious photometry is, at this moment, my main focus, my research led me to conclude that a mono camera and filters was where my budget could go. If I was just casually wanting to do photometry, and accepting that there are limitations, then a colour camera would be just fine.

Whew, this getting longwinded. You did not ask a specific question, so the best I can offer about the type of imaging equipment to get is to get the camera that allows you to do what you specifically want to do, and then also accept that you just might need another camera down the road to meet different expectations.

[emranismail11]

I think that someone just starting to think about photometry should just use what they have to start with . Almost any rig can be used to do some photometry. One issue I personally had to face, and I still have not fully dealt with, is what do I want to accomplish. If the goal is to just do some eclipsing binary timings of brighter stars you will have a relatively easy time getting started. If the goal is to detect exoplanet transits, then greater demands on the equipment and technique is made. 

 

I am assuming that you are just starting out in the game ( you mentioned you want to start astrophotography soon) and with , literally, the whole universe beckoning, it is easy to see so many interesting things to do. In my own case, I wanted to do it all- lunar, planetary, solar, DSO, photometry, and so on. The thing I found is that no one setup can do it all at the highest levels, but most setups can do it all at some level. I found that my expectations needed to be examined as to what was achievable with my experience level, time available and budget. Unrealistic expectations caused me to be disappointed as I was not producing APOD images. After some time, and growing experience, I forced myself to examine these expectations. The point is that my expectations of what I wanted to achieve should drive what type of equipment I needed and the time I needed to devote to any particular aspect of the hobby. 

 

I think you have made a good choice of mount, the Atlas, as it is the foundational piece for anything you do. You have (or are getting) an 8" SCT. This is a popular choice as a very versatile scope. I have a C8 and have done lunar and planetary imaging and I think you will enjoy that. While I have done some DSO imaging, I have found that very challenging with my HEQ5 mount and such a narrow field of view. I have only started my photometry work but I found that the 8" and HEQ5 along with a monochrome 533 camera to be a very workable combination, but after some years of other types of imaging.  My initial results have been good, so I think you can do so as well. However, I have taken the AAVSO courses on Intro Photometry and using the AAVSO software, Vphot, and that was the time investment . In deciding that serious photometry is, at this moment, my main focus, my research led me to conclude that a mono camera and filters was where my budget could go. If I was just casually wanting to do photometry, and accepting that there are limitations, then a colour camera would be just fine. 

 

Whew, this getting longwinded. You did not ask a specific question, so the best I can offer about the type of imaging equipment to get is to get the camera that allows you to do what you specifically want to do, and then also accept that you just might need another camera down the road to meet different 

Thank you for the response, so I actually just recently bought a player one ares m(533mm) camera, in the process of getting everything I need to start doing some amateur research. For now, I plan on getting a V filter for now, and an lrgb set for imaging. 

[Ed Wiley]

Remember, you need to cover the rig to make sure there are no light leaks when you take dark and bias frames, or, you need a blank filter in the filter wheel. I'm remote, so its a blank filter for me.

Ed.

[Xilman]

Remember, you need to cover the rig to make sure there are no light leaks when you take dark and bias frames, or, you need a blank filter in the filter wheel. I'm remote, so its a blank filter for me.

Ed.

I'm local but a blank filter is so much easier. With an 11-position FW I can afford to be extravagant. Some of the filters , LRGB, never get used anyway except on exceedingly rare occasions.