Refractor Setup

Comment

Comment by Robert C. Mills on October 30, 2011 at 4:55pm

It's a very nice set up. I like the cameras and scopes as this is much like mine. We get what we can afford and do the best we can. The SBIG seems good to me. You have the option of using a separate guider or dual chip. I like having multiple options at my disposal.
Long downloads are OK with me as I shoot 10-15 minute subs and I can wait 23s on top of that. I currently use an SXV H9 , QSI 540 and SBIG ST8300. I used to use a parallel port SX MX9. It was really slow, but I had fun and got nice images. I have also shot with my Canon where I would shoot 10 minutes and then wait for 10 minutes for the Internal Dark to be measured and subtracted and then the image downloaded.
I think your set up is just great.

Comment by Richard Crisp on May 19, 2011 at 6:08pm

their cooling is not very good. Their readout time is the slowest in the industry: how do you shoot sky flats with 23second downloads and a sun setting? Their read noise is comparable to their competitors so the slow speed of the readout/download seems to be just a bad idea.

I don't see why I need to buy such a limited performance camera in order to get a guider when I can buy an OAG and connect it to any camera....

If I need an off axis solution for a long focal length I have it with the external OAG. Normally I use piggybacked refractors with a separate guide camera. I just regard the integrated OAG as just an expensive gimmick that is completely unnecessary....

I get fine results using the methods I have been using for years...

Comment by Charles Dunlop on May 19, 2011 at 5:56pm

point made. I don't use. How you like those QSI imagers with the light picked off to guide with? That's a much better idea it seems.

Comment by Richard Crisp on May 19, 2011 at 5:48pm

at the time when SBIG created their first self guided camera CCD chips were very expensive, even the tiny ones

so it sort of made sense. Plus no one did emission line imaging... I brought that to the party a few years later

but now the price of a big CCD like the 16803 is about $4000 and a set of big filters to cover it (lrgb +s2HaO3) is actually more depending on the brand you buy

then looking at the STX that uses the 16803 and self guided, you need 65x65 mm filters to cover it but everone else's 16803 camera can cover the big sensor (36.8mm on a side) with 50x50mm filters. The price of seven 65x65mm filters can be a fair amount more than the sensor itself and as you are finding out it isn't necessarily easy to guide through a filter.

I think it was a great idea when everyone used SCTs with mirror flop but those days are gone and also the economics of filters versus CCDs has also changed too.

So in my assessment that was a good idea but it has passed its prime

most people I know don't self guide their STLs yet they paid for that unused guider chip. It just seems like a dumb idea to pay extra for something that is not very useful, especially for a 16803 sized sensor that forces you to use HUGE filters that are very expensive

Comment by Charles Dunlop on May 19, 2011 at 5:18pm

It's a good point. I'd had it in my mind that I'd never buy a dual chip camera again already. Only thing that could change that is if there's a lot of light coming in because of a large aperature or if the light is picked off in front of the filter. If I was using a one shot camera like Trevor is, I'd use the dual chip. Anyway, you got me thinking about trying it out again with a longer guide exposure time now that I can go unguided for minutes, I can think og the guider differently, and perhaps go with like a 5 second guide expsure. I'll try it at the end of my clear skies next week, maybe like the last night or something.

Comment by Richard Crisp on May 19, 2011 at 5:11pm

my first camera was an ST7E parallel port. I quickly got frustrated with its low resolution and finally bought a better camera and now still use it but for guiding

I found that guiding behind a filter was not easy, and was compounded by a small FOV of the guider chip etc.

Once I began seriously doing narrowband i abandoned the self guiding and have never looked back

for camera lenses or very short focal lengths (less than 600mm) maybe it makes sense for LRGB but in my experience it is difficult for long focal lengths (I did have an ST10XME too) or for emission line work it was really hard for me to consistently get good framing and have a guidestar I could use.

Most people I see using the self guided cameras don't use the guide chip. I always wonder "why spend the extra money if you aren't going to use the feature"...

Comment by Charles Dunlop on May 19, 2011 at 9:39am

yeah I might switch over. It's much easier obviously with the internal guide chip. Think it makes a lot of sense for me now. Maybe fiddle with it at the end of my clear skies patch next week.

Comment by Trevor Woodrow on May 19, 2011 at 9:37am

Gotta love the 'Gab!

Comment by Trevor Woodrow on May 19, 2011 at 9:36am

Charlie....when I was shooting M86 through my 102mm, with the LPR filter, I was having a hard time finding a guide star with the integrated guider. Then I realized that I could bin the pixels 2x which increased the sensitivity and increased the exposures to 10 seconds and it guided pretty well, with plenty of stars to choose from. I think it was Crisp that alerted me to all the resolution I was losing using the seperate guider and he was right. Before, I noticed over the course of a session, the fov did drift somewhat even though my guiding was error free. Now that I am relying soley on the internal, no issues at all, each frame is dead on and fewer errors.
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Comment by Charles Dunlop on May 19, 2011 at 9:10am

Well I originally got that camera because I loved the idea of an internal guider, but at the time was doing short guide exposures as my mount and alignment weren't super solid, and was behind a filter wheel, which short exposures was causing me to lose stars in various filters. So I gave up quickly and put my old guide scope back on.

But now that I'm doing longer guide exposures on a much better mount and better alignment, you bring up an excellent point. If I do 3 second guider shots I should be able to get a star behind each filter. And since I'm doing CCDautopilot that program is always picking it's own guide stars from one shot to another, perhaps I'll try it out again as less weight on the mount the better.

Thanks for making me rethink this one Richard. Man I love astrogab!!!

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