What's to lose? guiding 8" SCT for DSO

[iapa]

As there's not even nautical darkness now I thought I might have a play with guiding the 8" SCT on the CGEM-DX

Nothing to lose, and lots of negative experience to gain.

In 

is says ratio of guiding to image should be less than 4, this combo is 1.58

Supposed to be free and clear tonight so, I can at least try to see how far I can push it. Not expecting much in the way of results tho.

• C8 with 0.63 flattener reducer and ASI1600 gives a pixel scale of 0.61
• f5 400mm refract with 2x barlow and touptek mono camera image scale is 0.97
• PHD2 guiding
• SGPro for sequence and plate solving
• PoleMaster
• Starsense
• 3 pts goat's blood, and some chicken bones
• list of useful deities

4s exposures with PHD2.

 

[LightBucket]

I have done exactly what you are going to do with an 8" Meade SCT, but with 1.5 second guide exposures, and with PHD1 and got perfect round stars with 10-15min subs, and that was on a fork mount on a wedge.... I used a Canon DSLR with an old Meade DSI guide cam, and was imaging at 0.97"/pixel, and guiding at 3.5"/pixel....through an 80mm guide scope.

[iapa]

How far did you manage to stretch your exposures with the setup?

2 minutes ago, LightBucket said:

I have done exactly what you are going to do with an 8" Meade SCT, but with 1.5 second guide exposures, and with PHD1 and got perfect round stars with 10-15min subs, and that was on a fork mount on a wedge.... I used a Canon DSLR with an old Meade DSI guide cam, and was imaging at 0.97"/pixel, and guiding at 3.5"/pixel....through an 80mm guide scope.

 

[AKB]

2 hours ago, iapa said:

• 3 pts goat's blood, and some chicken bones
• list of useful deities

...this should clinch the deal, but, just in case, I'd suggest entrails also.

[michael8554]

It will be interesting to hear how you get on with 0.97 guiding, or whether you have to lose the barlow to get closer to 4 times imaging scale like Lightbucket.

Michael

[LightBucket]

1 hour ago, michael8554 said:

It will be interesting to hear how you get on with 0.97 guiding, or whether you have to lose the barlow to get closer to 4 times imaging scale like Lightbucket.

Michael

Yes, guiding at the pixel scale will be difficult to be honest....but worth a try, longer guiding exposures will probably be better to even out the seeing...

[iapa]

fell at first hurdle

don't have the right spacers for 110mm back focus required for the corrector and the DSLR wasn't available.

then it got hazy/cloudy over, just enough to be nice and murky

[Davey-T]

The 110 back focus isn't that critical, not like on a fast refractor, I found that somewhere around the quoted measurement worked fine.

You can buy an Celestron adapter to give the right spacing for a DSLR.

Dave

[iapa]

1 minute ago, Davey-T said:

The 110 back focus isn't that critical, not like on a fast refractor, I found that somewhere around the quoted measurement worked fine.

You can but an Celestron adapter to give the right spacing for a DSLR.

Dave

I'm not even close tho'

But it it's not that critical..... maybe if the thunderstorms clear tonight.....

[Davey-T]

One of these gets it close enough.

Dave

http://www.365astronomy.com/Celestron-SCT-T-Adapter-C5-6-8-9-1-4-11-14.html

[iapa]

4 hours ago, Davey-T said:

One of these gets it close enough.

Dave

http://www.365astronomy.com/Celestron-SCT-T-Adapter-C5-6-8-9-1-4-11-14.html

Been having a rummage in the 'I'm not sure why I have this' box and found similar, but it's 30mm. And I just realised that I got a 25-29 T2 extension to use of the flatteners for my refractor.

I've 20mm on the filter wheel.

That gives me abut 80mm.

And - as this is just an experiment