NGC3372 Eta Carina

[bloodhound31]

I am sure I can get a little more out of this one. I think I have gone rusty in my processing over the last few months of not imaging....

19 minutes with darks and flats.
Nexstar 11 GPS - Focal reducer to F6.3
Unmodded Canon 400D
Manual guide using Toucam on piggybacked ED80 on screen.
Stacked in Deep Sky Stacker and processed in paintshop pro 9.

[citivolus]

I'm curious about the distance from your reducer/flattener to the chip in your camera, as the image looks less flat than I would have thought it would be with that combo. Maybe if you could tweak that distance a bit, you'd end up with sharper results at the edges? The upper right in particular really shows coma. Baader makes some 7.5mm, 15mm, and 40mm spacers for t-adapters that might help get you closer. Look for their "T-2" extension tubes. Unfortunately I don't know of any similar products on the Australian market, but postage on these is really cheap from overseas.

Also, there seems to be a bit of field rotation there, most visible in the upper left and lower right. How is your polar alignment? I guess it could just be an artefact of the reducer combined with slight flexure in the imaging train making the coma present slightly differently in those areas, or maybe slight rotation in the stacking process.

Regards,
Eric

[citivolus]

A bit more info: The Canon EF mount flange to focal plane distance is 44.0mm. The most commonly seen number for the recommended distance for the Meade/Celestron 0.63 focal reducer is 105mm from the reducer to the focal plane, leaving you with 61mm to compensate for between the reducer and the flange. That is based on a 230mm focal length for the reducer, but you will see different focal lengths for this reducer floating around out there and would be best to measure that of your own.

Regards,
Eric

[Dennis]

Hi Barry

Good effort although as Eric noted, it’s not quite as flat as it should be at the edges? Some very nice detail in the nebulosity, the pillars are quite dramatic. Great image scale by the way, quite a tough job to achieve.

Cheers

Dennis

[bloodhound31]

Hi Eric, so are you saying I need to get the camera chip closer or further away from the focal reducer?

[citivolus]

Yes, one of the two :) It will result in a much flatter field, giving you focus at the centre and edges simultaneously. How far is it currently between the back of the reducer and the front of the camera?

Regards,
Eric

[bloodhound31]

I will have to go and measure it mate. I have the FR screwed onto the back of the scope, then the visual back. I took the eyepiece adapter end off the camera adaptor and screwed it directly into the t-ring so the whole thing only pokes out from the front of the camera about an inch. That then slides straight into the visual back.

I dont know how I could get it much closer unless I do away with the visual back and eyepiece adapter, then find a way to screw th et-ring straight onto the focal reducer.

[EzyStyles]

beautifulllll shot barry. havent heard from you in awhile! colours are great also . that bit of coma around the edges can be easily cropped out ;)

[bloodhound31]

Eric, reference that the field curvature on my Eta Carina image (already cropped) are you saying something to do with the distance of the sensor chip in the camera, to the surface of the lens in the focal reducer?

I measured mine as close as I could with a vernier depth gage and got a total distance of 92.5 from the filter immediately in front of the sensor (right inside the camera with the mirror flipped up out of the way to allow access) to the surface of the focal reducer.

Here are some pics of the current set up with distances marked on the photos.

I'm sure I can do something to increase the distance to experiment, but getting any closer is going to take something special.

[jase]

Keep up the great work Barry. A significant improvement on your previous posts. You're heading the right direction.

[Lester]

On ya Barry.

Nice colours in the nebula.