NGC 253 in Narrowband

[ejcruz]

Still learning the ins and out of this GSO RC 8", had to machine a home made bracket to mount the guide scope, have also replaced the focuser with a FeatherTouch. Tried to collimate using CCDInspector but it was flipping between 0.5 to 6 without any adjustment, at the time FWHM was about 4, tried both multi stars (focused) and single star (out of focus), so this image was captured with the RC collimated using the Glatter - the holographic image looked pretty good to me. I then had to go through another learning curve guiding with PHD as I'm now imaging at 0.68 arcsec/pixel. Further this is the first time I've experience dew on the main mirror, so some of the subs in this image had dew, just wondering if a dew strap can be used on this fibre casing of the RC.

Following is a result of NGC 253 captured from my backyard.
Main Scope: GSO RC 8"
Guide Scope: SW 70mmx500mm
Main Camera: QHY9 mono
Guide Camera: QHY5 mono
Subs: Sii 8nm 16x20min Bin2, Ha 7nm 17x20min, Oiii 8.5nm 11x20min Bin2
MPCC Field Flattener
HEQ5 Pro Mount
Neb2 and PHD
Processed using IP and PS-C3
Hubble palette Sii=red Ha=green Oiii=blue

Small version
http://ejcruz.smugmug.com/Photography/Nebulas/Forum-Post/CVNGC253SHO-1FlattenCrop/689902360_5a6dt-L.jpg

Large version
http://ejcruz.smugmug.com/Photography/Nebulas/Forum-Post/CVNGC253SHO-1FlattenCrop/689902360_5a6dt-X2.jpg

Advise always welcome.

Cheers
Eddie

[Paul Haese]

Guiding looks really good.

Do you have the three extensions on the back fo the scope? You don't seem to have any sag issues like I have been getting.

Imaging at longer focal lengths is very challenging.

[strongmanmike]

Interesting Eddie...? many have trouble coming to terms with NB nebula shots so they will have a lot of trouble accepting a NB galaxy image for sure.

Not sure I'd consider spending 12hrs imaging a galaxy in NB, not sure it works that well visually really :shrug: perhaps it's just the lack of familiarity, should lots of people start doing it perhaps it will look more ..?..fashionable? :lol: but 253 is a nice bright galaxy to experiment with though.

The exercise certainly honed your guiding skills and on a HEQ5 too :eyepop:

Mike

[multiweb]

Sculptor in NB? That's interesting. I didn't think much would turn up. I quite like the colours you got. Nice guiding too. :thumbsup:

[ejcruz]

I have the 2 RC extensions plus an additional 50mm extensions, yes the FT took care of the sag, it's a top class focuser, I'm so impressed I order another FT for my FLT110:D have you tried using dew strap on your RC?

I suspect your correct about NB galaxy :lol: but I purchased the RC to mainly capture galaxy so I decided why not have a go in NB.

Cheers
Eddie

[Paul Haese]

Eddie I have not tried using a dew strap on the outside of the RC. I have noted lately that I am getting some dew forming on the primary after 5 or so hours of imaging. I used a small strap around the secondary some time ago and found it to be more trouble that it was worth. It effective reduced the brightness of objects and made the spikes look a little weird so I took it off. In really dew ridden conditions the scope struggles with keeping it at bay. Looks like another suggestion for Jim sheng coming on. An internal dew heater for the secondary might work well. Not sure about the primary. The glass must be very thin to end up with dew on it, otherwise it would continue to release heat all night.

[Kal]

Interesting. I can't recall ever seeing a galaxy imaged in NB before. The result you got is fantastic though, the dust lane features are very prominent. Well done and kudos for thinking outsode the square! :)

[ejcruz]

I should be able to capture more details once I nail the dew issue on the primary and secondary mirror, would prefer to use the SW 80mmx400mm for the guide scope but HEQ5 Pro is having probs handling the weight.

I didn't think of checking the secondary because it points backward and down so another thing to look at, dew on the primary had me going for some nights thinking I had collimination probs.

It's an interesting experiment.

Does anyone have any advise in using CCDInspector for collimination.

Cheers
Eddie

[jase]

Interesting! Tip o' the hat to you Eddie for giving it a shot. I guess you now know that answer... Galaxies are wide band spectra targets, similar to clusters. If you're keen to use narrowband on galaxies, stick with Ha to emphasise the HII regions in a traditional RGB data set. Chris Schur did a presentation at AIC2007 on the topic which maybe of interest to you.

http://www.schursastrophotography.com/powerpoint/AIC2007.ppt

All this aside, don't waste the data. You can always do some synthetic channel work to produce a psuedo RGB. It would probably turn out a stunner. Your stellar profiles are as tight as I've seen from the GSO RC8, undoubtedly due to the narrowband filters reducing bloat.

Cheers

[ejcruz]

Many thanks for the link, very interesting and very helpful, lots to think about.

Cheers
Eddie

[Bassnut]

What was the motivation for NB on a galaxy?, as Jase and Mike point out, stars are a broadband scource, and not suited to NB. The colour layers look odd and sharply differentiated. Ha for small stars blended with RGB would work, but not pure Ha:SII:OIII.

The latest version of CCD inspector has a 1 star collimation feature that I found works a treat.

[LGT150]

je trouve cette représentation originale et pleine de détail.
Lucien

[Moon]

Eddie

I still prefer your NGC 6188 (http://ejcruz.smugmug.com/photos/623944560_UDZyy-X2.jpg) image :P , but the guiding here is much better. Very well done!

James

[ejcruz]

I used NB as experimentation because I still haven't purchased RGB filters:D I must give the 1 star collimation another go, the glatter and it's holographic is very handy.

Hope you enjoyed it! :)

I started capturing NB for a moasic on this but now will have to wait till next year to complete.

Cheers
Eddie

[gregbradley]

Hey that's different. Nice round stars and those GSO RCs are proving to be a super buy.

Greg.