Galaxy cluster in Pegasus

[Jon (Jonathan)]

I can count 16 galaxies in this image, roughtly 50' x 50' centred on NGC 7619 in Pegasus. The brightest orange blob in the bottom left corner is a 6.9 mag star across the border in Pisces. It's only 2 hrs of exposures with the 60Da; clouds rolled in and spoiled another 2.

[lazjen (Chris)]

Neat. Only 16?

The stars seem a bit weird in places, like the top right for example - they look like mini half-moons? What's happening there?

[Rex]

Hi Jon, great image and you've managed to show quite a bit of detail for 2 hrs of data, well done. As Chris mentioned some of your stars are funny shapes. I don't really have the experience to give you any idea's as to why that is. To me some look like focus issues, some look like field rotation from polar alignment being slightly out, and some look like coma. So I'm not much help there I'm afraid. Hopefully someone with more experience will have a better idea. Good job.

[Jon (Jonathan)]

Originally Posted by lazjen

Neat. Only 16?

The stars seem a bit weird in places, like the top right for example - they look like mini half-moons? What's happening there?

I've found 20 now.

The half moons are coma, I think. This morning disassembling the telescope I found the lens in the field flattener a bit loose in the housing. The
At probably has something to do with it. But I've always found a bit of coma in the corners when using the big 22mm chip on the DSLR with the f/6.3 reducer.

Also PA was a bit quick and dirty.

[Jon (Jonathan)]

And, now I look at it, is seems to me collimation is a bit out.

[renormalised (Carl)]

Jon, what scope did you use to take the shots with? Depending on the scope you've used, it looks like you have a bit of coma there as well as having the camera possibly slightly off axis. I'd also check how tight your tracking is as well because you have a tiny little bit of field rotation there. The focus also looks off.

[Jon (Jonathan)]

I used the 10" SCT with the f6.3 reducer/flattener

[renormalised (Carl)]

If the flattener is a little wonky, that will intro the coma. Although, is your scope an ACF scope? If that's the case your reducer/FF might not work with the optics. ACF optics is touchy with flatteners and you have to have one that's made for the ACF optics. Normal fatteners/reducers will intro coma into the system. You should see it when using the Meade .33 reducer/flattener. Looks like the scope's jumped to warp!!!

[Jon (Jonathan)]

No, not an ACF scope. Just the standard LX200 - so some coma comes just with the optics, I assumed - otherwise why bother bringing in ACF?

I think you are right also that focus wasn't great, and PA was out. This one was quick and dirty.

[blink138 (Pat)]

nice pick mate!........ i count 20+
pat