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#1 Hubert

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Posted 30 June 2013 - 05:43 AM

Is someone on this forum doing photometry with a AGBcamera?

I had a SBIG ST7 but I sold it a while ago ( to a forum member ) because I wanted to do something else in astronomy. I have done some other observing but now it seems that the variable disease is back on me. I think it's in the blood. ;)

Because SBIG is no option for me ( it's to expensive to buy a new one or a used one ) I'm looking for a other camera. The other commercial available camera's are almost AGB. I have read in the past that one can do good photometry with a AGB camera as long I don't go above the linearity.

So, which brand is good choice?

#2 rutherfordt

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Posted 30 June 2013 - 10:49 AM

Hubert:

I have used both the Meade DSI Pro I and Pro II for photometry and they worked just fine. As you have already mentioned, just keep them in the linear range and all is well.

Tom

#3 Hubert

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Posted 30 June 2013 - 11:34 AM

Hello Tom,

what is your setup? How faint can you go with it?

With my ST7 and C8 I could reach mag 13 and had very good counts with exposuretimes of about 2 - 3 minutes. Most of the time I did unfiltered exposures of High amplitude stars.

#4 jgraham

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Posted 30 June 2013 - 03:36 PM

I have used each of the DSI Pros (I, II, and III) for photometry and spectroscopy. They are pretty liesr out to about 50,000 counts or so. Just to be safe I generally tried to keep my reference and variable stars below 32,000 counts (half full-scale). With the DSI Pro III on my SN6 (6" f/5) I can reach magnitude 17.5ish using 60 second exposures. I'll be switching over to an SN8 for my photometry (8" f/4) and it'll be very interesting to see how well it performs.

#5 Hubert

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Posted 01 July 2013 - 12:50 AM

Hello John, that are very voor results.

#6 rutherfordt

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Posted 01 July 2013 - 07:35 AM

Hubert:

Back when I used the DSIs, my setup was the same as John's-- a Meade SN6. Its been a few years so I don't remember exactly how deep I could go. I was not able to get 60-second images, though-- because of the mount, I stacked several shorter exposures which may have totaled 60 seconds (I don't remember).

I have recently acquired an ST7, but have not yet used it for photometry-- I mostly do single-channel photometry with an Optec photometer these days.

Tom

#7 Hubert

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Posted 03 July 2013 - 01:49 PM

I made a decision.

I'm going to buy a SBIG ST-402ME. It's the same as the ST7 I used to have expect the autoguiderhead. That's no problem because I can use a extern autoguiding system. I also think that one of the advantages of the ST-402ME is that I can buy a intern filterwheel with photometric filters (BVI).

My question now is: what is the best system to autoguide?

Standalone or a guidecamera connected to a laptop?

Pro's and con's?

#8 Ed Wiley

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Posted 03 July 2013 - 09:22 PM

Good choice -- I use a ST402ME with the BVI filter wheel on a SN 8" F/4. It give a very useable FOV and the camera is very sensitive. I don't think you could make a better choice even if you spent more $$. I have a fairly good mount and use a WO 66mm with a DSI Pro and PhD for guiding. The WO66 is very solidly mounted (no rings). Everything is hooked up to a Dell Latitude running System 7.

Clear skies,
Ed

#9 Hubert

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Posted 04 July 2013 - 02:09 AM

Hello Ed, thanks for the advice.

I use a C9.25 which gives no big FOV but it's also usable because I always go after stars between magnitude 10 and 15.

What do you mean with the WO 66 very solidly mounted? How do you do search for a guidestar with no rings?

#10 Ed Wiley

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Posted 04 July 2013 - 01:47 PM

Hi Hubert:

The little WO66 is clamped down on a rail, adjusted to "kind of" point in the same direction as the scope. The FOV is wide enough that I have not failed to fine a guide star yet. Note the "yet." :grin:

Ed

#11 Hubert

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Posted 04 July 2013 - 02:24 PM

If I understand correctly you can pick any star in the FOV of the guidecamera? I don't know how this is working. I assumed that you had to point the guidescope to a bright star?

#12 gavinm

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Posted 04 July 2013 - 03:24 PM

After years of using the built-in guider on an ST7 (which has a very small FOV), I've never had to rotate the camera or re-center it to find a guide star. There is always one visible, even in this small FOV. MaximDL detects automatically the brightest in the FOV or you can select one manually by clicking on it. This is the advantage of having a sensitive, cooled guide camera.

#13 Hubert

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Posted 05 July 2013 - 01:29 AM

Yes, Gavin. I also think that this is one of the advantages of the extern guidecamera. Thanks for pointing this out.

#14 Ed Wiley

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Posted 05 July 2013 - 05:57 PM

Hi Hubert: Yes, I use PhD so I can pick any star in the FOV for guiding, no need to have the guide star in the center of the FOV.

Ed

#15 Hubert

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Posted 06 July 2013 - 04:33 AM

Hi Hubert: Yes, I use PhD so I can pick any star in the FOV for guiding, no need to have the guide star in the center of the FOV.

Ed


Looks easier than using intern guiding. There was centering the guidestar a difficult :bawling:

#16 Ed Wiley

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Posted 07 July 2013 - 11:10 AM

Hubert: I don't think this is particular to PhD using a guide scope, I think must guiding routines allow you to pick any star in the FOV of the guide chip. With the ST7 cited by Gavin ("internal") it would defeat the purpose of centering the target if you had to center the guide star.

Ed

#17 gavinm

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Posted 08 July 2013 - 01:08 AM

Yes, the guiding window in MaximDl shrinks down (for faster downloads - to maybe 100x100 pixels?) so I wouldnt know if my guidestar is centred or somewhere near the edge. It doesn't matter - it just works automatically.

#18 Hubert

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Posted 08 July 2013 - 01:19 AM

When I used my ST7 I always centered the guidestar in the center of the field. It was a small field and the calibrating is done in a big part of the field. If the guidestar would be not near the center I think that it was more difficult to calibrate.

#19 gavinm

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Posted 08 July 2013 - 03:16 PM

I am the opposite. I always had to frame my main CCD carefully to get the right comparison stars into the frame. My target wasn't usually centered and I took whatever guidestar I could. Always worked.

#20 Hubert

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Posted 14 July 2013 - 04:32 AM

One thing that is holding me back of buying that ST402 is the small field of it.

I have some doubts. Or I buy the NAGB with a small fov or I buy a AGB with a bigger fov.

Someone have comments on this?

#21 gavinm

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Posted 14 July 2013 - 09:53 PM

As mentioned above, I've never had a problem with the small FOV of the ST7 at f6.7. Larger would be nice, but I'd choose more sensitivity of the NABG over a larger FOV any day.

#22 Hubert

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Posted 15 July 2013 - 08:47 AM

Hello Gavin, you are right.

And I always can sell my C9.25 and buy a 10" newton f4 which gives me a bigger FOV.

#23 Ed Wiley

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Posted 16 July 2013 - 12:12 PM

Here is what to do: figure the FOV for your optical path and the CCD. Go the the AAVSO and download some CCD charts scaled to that FOV. If you find you have enough comp stars in that FOV then you are good to go. For example: I image at F4 with the 402ME. My FOV is 30'x21' which is great for my program of Miras and eclipsing binaries and fine for asteroids.

But, nothing wrong with larger FOV and ABG cameras so long as you figure linearity and stay linear.

Ed






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