NGC 1566 a Barred Spiral Galaxy in Dorado

[Dennis]

Hello,

Here is a lovely looking galaxy; NGC 1566 a Barred Spiral Galaxy in Dorado, as recorded by the C9.25 at F6.3 with the ST7 CCD camera. After spending the evening chasing Minor Planet 2008 TT26, I only had time for 3 x 15 minute exposures before the twilight of dawn chased me indoors.

Magnitude: 10.30
Size: 8.5'x 6.2'

Thanks for looking!

Cheers

Dennis

[sjastro]

Nice image Dennis.

One of my favourite galaxies.

Steven

[Dennis]

Thanks Steven – I’m trying to work my way through some of the smaller DSO stuff that is ideal for the image scale of the C9.25 with F6.3 Reducer/Corrector and the Mewlon 180 with its 0.8 Reducer/Flattener and the ST7.

Cheers

Dennis

[strongmanmike]

Another nice galaxy image Dennis, always nice to look at.

I notice that many of your framings don't have the galaxy in the centre of the frame, is this because of the difficulty finding a guide star with the self guide feature..?

Keep posting I love seeing different galaxies even if only in b&w.

Mike

[[1ponders]]

Nice Dennis :cool2:

Have a try at NGC2442. I shot it the other night through my 8" with a 0.5 reducer and had plenty of room left. It might be a bit of a squeeze with your 9.25 but it would look good. ;)

[Ric]

Nice capture Dennis, the formation of the spiral arms looks wonderful.

[strongmanmike]

Yeh NGC 1097 and NGC 1398 are pretty cool too in that general area

Here is a short exposure of NGC 1398 I did two years ago from light polluted skies right behind the Australian War Memorial in Canberra:

http://www.pbase.com/strongmanmike2002/image/67797607/original

A nice long exposure with a sensitive camera like yours from dark skies would look beautiful I recon? If the seeing was good too there should be even more subtle detail than this image shows..?

Mike

[Kevnool]

Fanastic barred spiral Dennis will note this in the next obs night.
Cheers..Kev.

[Hagar]

Very well captured Dennis. A lovely balanced spiral well worth a couple of hours of RGB data.

[Dennis]

Hi Mike

Thanks for the nice words of encouragement!

I’d like to think it is the artistic side in me, following the proportions of the Golden Mean to create the perfectly balanced composition but alas, you’ve hit the nail on the head, it’s the size of the TC211 guide chip, a paltry 192x164 pixels that tends to dictate where the target will appear on the main chip.:(

I did get to use Gerald’s SBIG ST4000XCM on the last evening at the Qld Astrofest and I was absolutely spoiled with the ST237-sized 640x480 guide chip!:eyepop:

I have tried my hand at off-axis guiding but at focal lengths of over 1500mm, I haven’t been too successful yet, with maybe 1/3 of the frames showing signs of slight elongation, so I would need to do some more analysis and work to chase this down.:sadeyes:

In the meantime, I quite happy poodling along with the ST7 and learning how to process mono data before I join you big boys in the rarefied, stratospheric realms of megapixel LRGB imaging, with it’s plethora of challenges to overcome; the sheer expense being one major hurdle right now.:whistle:

Cheers

Dennis

[Dennis]

That’s a superb NGC 1398 - a beautiful sky background and gorgeous tonality throughout, with not a hint of noise – that’s the direction I’m trying to head in!:scared:

Cheers

Dennis

[Dennis]

Thanks Paul, Ric, Kev and Doug – I’m slowly learning the black art! More importantly, I’m beginning to enjoy it!

Cheers

Dennis

[strongmanmike]

Funnily enough I have rarely been aware of any issues with piggyback guiding. Whether with my 600mm FL ED80, 1500mm+ FL 12" LX200GPS (fork mounted!) or the 1140mm FL AP on the laser guided NJP :shrug: I have done nothing but piggyback guiding. Of course I have rarely gone over 10min exposures so perhaps at 2000mm+ FL and over 10min exposures there may indeed be an issue with differential flexure but still, I think self guide is waaaaaay overated. The vast majority of high end users don't self guide anyway for exactly the reasons you are finding. I use a rather sensitive SXV-h9 which has a good sized chip for guiding (9mm X 6.7mm) and I have NEVER had to move the guide scope to find a guide star..?

Have you tried piggyback guiding?

Mike

[Dennis]

Hi Mike

I’ve tried a side-by-side set up and that is where I seem to hit a few problems in stellar elongation as well as field rotation.:(

I used a solid, 6mm thick aluminium plate as the side-by-side mounting plate, with a WO Losmandy Style saddle and plate and some WO guide rings bolted directly onto the plate. The guide scope is a WO 66mm F7 Petval and I use an (old model) Orion Star Shoot Deep Space (cooled) CCD with PHD guiding and PHD reports guide star adjustments of the order that “shouldn’t” show up as trails in the imaging set up.:shrug:

As soon as I poke my head above around 1400mm and 3 minutes, bang, I get star elongation. I confess to not having logged and analysed any guiding data yet, as I’ve focused on the mechanical rigidity and balance issues first. I guess my main failing in this process has been to step back and analyse the data to see if that can suggest a cause, or two!:doh:

When I fit then strip the side-by-side paraphernalia down and just fit the OTA on the mount (EM200) and fit the ST7 (765x510) directly to the OTA, the elongation vanishes? I can go as long as 30 mins (best so far), at 1400mm with no trails and no field rotation. In fact when the image downloads, I often have to check that it did so, as there is no discernible movement between successive frames. Or at least if there is, it’s at a sub-pixel level?

Over the last couple of (frustrating) years, I’ve gradually removed some of the contributing factors by using heavier hardware, better tying and managing cable runs, balancing around both axes, having the mount slightly heavy against the RA drive, tweaking guide settings in the software, adjusting the worm on the EM200 with a wooden mallet (http://www.astro-physics.com/index.htm?tech_support/mounts/600gto/600ebacklash), etc. and whilst this has almost removed any trailing when using the ST7 in dual chip auto guide mode, I just haven’t had the same success with the side-by-side arrangement.:shrug:

I could try mounting the guide scope on the C9.25 as I have the ADM rings and mounting rail, but on the Mewlon 180 I’d have to purchase a set of OTA rings to do the same.:scared:

Like you, having to set up and tear down each night isn’t much fun, so I’ve shied away from long fl DSO stuff until I got my second wind, recently.:(

I really need to log some data and understand the source and magnitude of the errors so I can better remove them, rather than thrashing around as I have been doing. Better still, a permanent set up eh!:thumbsup:

Cheers

Dennis

[Jen]

;) nice pic Dennis :thumbsup:

[Dennis]

Thanks Jen – glad you liked it. It was a nice way to end a very productive all nighter, although dawn arrived a couple of hours too early, I was still feeling fresh!

Cheers

Dennis

[Jen]

Awww yes Dennis its great to be able to stay up and do an all nighter now without having to freeze our butts off :P
:cool::cool: