A dusty Starfield near M8

bmitchell82 (Brendan) · #1 02-04-2010, 06:02 AM

Well doing a bit of testing to confirm that i have at last rid myself of that stinking pesky astigmatism here is a 1 min shot of a star field near the lagoon nebula.

5 x 60 second @ ISO 3200
Canon 40d 10" dobsonian
DSI2 + Finderguider
EQ6pro + PEC

http://s700.photobucket.com/albums/w...starfieldt.png

Ide love people to critique my collimation, flatness of field, vignetting, that kind of stuff, this photo wasn't taken for its pretty factor

strongmanmike (Michael) · #2 02-04-2010, 06:38 AM

Well Brendan I can't see anything wrong with that as far as the stars go, they look nicely round to me..? There looks to be slight vignetting in the corners though but it's hard to confirm.

Mike

jjjnettie (Jeanette) · #3 02-04-2010, 07:13 AM

Could you give us a full res crop from each corner please?

bmitchell82 (Brendan) · #4 02-04-2010, 10:48 AM

Thanks for your replys

that is a edge to edge with the only cropping coming just to trim the stack edge. if what your asking for is a bigger resolution (remembering full res is 57mb

). Let me know if you want a bigger picture.

Mike:
i am sure my collimation is still slightly off, either that or the secondary is slightly (and i mean slightly) off to the rhs hence the darkening into the LHS. I will be ordering the infinity xlk and needed gear from cats eye next week so hopefully i can get it perfectly nailed.

you don't know how many hours i agonized over finding that source of pinch!

DavidU (Dave) · #5 02-04-2010, 10:59 AM

Looking good mate. Did you go for an oversize secondary to make sure you have a fully illuminated field?

bmitchell82 (Brendan) · #6 02-04-2010, 11:06 AM

yes i did, i would have gone for a 75mm secondary but my options at the time are 70 or 88. 88 was too big and would have caused a 38% CO, as it is the 70 rolls in at about 27% CO which for my liking is perfect.

the difference is a 8mm fully illuminated circle out to 36mm@ 75% illumination, where as now its 24mm fully illuminated circle out to 58mm @75%. For the cost it was a no brainier!

DavidU (Dave) · #7 02-04-2010, 11:18 AM

Very tidy Brendan. I want to do this with a 12" but use cage/truss construction. It's all just $$$$

Quote:

Originally Posted by bmitchell82

yes i did, i would have gone for a 75mm secondary but my options at the time are 70 or 88. 88 was too big and would have caused a 38% CO, as it is the 70 rolls in at about 27% CO which for my liking is perfect.

the difference is a 8mm fully illuminated circle out to 36mm@ 75% illumination, where as now its 24mm fully illuminated circle out to 58mm @75%. For the cost it was a no brainier!

bmitchell82 (Brendan) · #8 02-04-2010, 11:24 AM

the conversion was extremely cheap, at 62 dollars delivered.