The Draco Dwarf Galaxy

[Knight of Clear Skies]

Prepare to be very underwhelmed.

Fancied a change after two nights attempting to guide for the first time (made decent progress but wasn't able to take a proper image), so I decided to have a go at imaging the Draco Dwarf galaxy with my 200mm f2.8 lens, a satellite of the Milky Way. It's one of the largest galaxies in terms of angular size, a bit bigger than M101, but is very dim. Its total luminosity is less than many stars in our galaxy, about a 5th of Deneb for example. My expectations were low and I wasn't even sure if it was possible. Here's the entire frame, the bright star at lower right is the close double Nu Draconis or Kuma, part of the head of the Dragon:

 

(Larger version here). Capture details are 29x1min unguided subs, flats and some 'fridge darks'.

Here's a 1:1 crop centred on our elusive dwarf:

Just visible is a concentration of fluff. Its appearance is that of a dim star cluster, most of its stars formed 10 billion years ago. It's very difficult to find any amateur images of it but I did dig out a couple eventually. Here's one by John Moore (no capture details unfortunately) and another by Alessendro Magi. If anyone can find any more I'd be interested to see them.

The above is just straight out of DSS, mono, inverted and with some careful curve stretching to bring out the faint stuff. I'll post up the colour starfield when I've had a chance to process it properly.

Not much of an image I'm sure you'll agree but this was a fun experiment for me.

[ollypenrice]

Well done. As you know, you've inspired me to have a look at this and it's in the can unprocessed. It's good not just to shoot the showcase stuff but to use the camera to do observing at the very limit as well.

Guiding seems to be going well, too.

Olly

[Martin Meredith]

I agree, good to hunt down these targets. I can just about see a darkening in the central region. And in any case I love these images showing such a density of stars -- puts some perspective on Earthly things... 

I had a go last year in observation mode with the Lodestar but just 8 minutes worth of 15s subs, so I was even more wildly optimistic and nothing much showed up, but I plan to try again and leave it for a really good night and a longer observation. It corresponds to middle quarter or so of your 1:1 crop as far as I can make out, oriented with N to the left.

The dwarf fills nearly the entire frame in this shot and it is interesting to see some background galaxies through the Draco Dwarf itself! The spiral in the top left corner is mag 15 UGC 10811.

Martin

[wimvb]

Great! The dwarf shows up quite large in my sky atlas, but as you showed, it's extremely weak. With the 200 mm you should be able to take longer subs, even without guiding. I think the target requires it.

Olly, I believe these were from unguided 1 min subs.

[Knight of Clear Skies]

On 07/05/2016 at 10:18, ollypenrice said:

Well done. As you know, you've inspired me to have a look at this and it's in the can unprocessed. It's good not just to shoot the showcase stuff but to use the camera to do observing at the very limit as well.

Guiding seems to be going well, too.

Olly

I look forward to getting a proper look at it.

On 07/05/2016 at 10:47, Martin Meredith said:

I had a go last year in observation mode with the Lodestar but just 8 minutes worth of 15s subs, so I was even more wildly optimistic and nothing much showed up, but I plan to try again and leave it for a really good night and a longer observation. It corresponds to middle quarter or so of your 1:1 crop as far as I can make out, oriented with N to the left.

I'm pretty sure you've got some of it there, counting faint stars there are more centre-right than there are in other parts of the frame.

23 hours ago, wimvb said:

Olly, I believe these were from unguided 1 min subs.

That's right, I was trying to guide an ED120 on an NEQ6 with limited success. Had it guiding (poorly and briefly) on Arcturus but not after slewing to my imaging targets. Solved some problems but it's a learning curve for me.

[wimvb]

I noticed that the background in your images has a pattern. Dithering would destroy this pattern allowing you to stretch more agressively.

Just a thought

[Knight of Clear Skies]

Yes, it would probably have benefitted from more of a dither. There is some due to the sub-pixel trailing in the subs, the camera is on a ball head joint so I get movement in RA and Dec. Typically this is enough for me, but with better polar alignment than I've had in the past and such a faint target I'll have to bear this in mind.

[ollypenrice]

Sorry, my mistake on the guiding. I took the opposite approach and went for 30 minute subs. I'll check them out this morining.

Olly

[astro mick]

I love the unusual,so refreshing to get away from the lollipop objects.

Well done.

Mick.

[wimvb]

 

Sorry, my mistake on the guiding. I took the opposite approach and went for 30 minute subs. I'll check them out this morining.

Olly

30 minutes, that should do justice to this target.

Happy hunting,

[Knight of Clear Skies]

6 hours ago, ollypenrice said:

I took the opposite approach and went for 30 minute subs.

Olly

I just used whatever I could get working and a naive sense of optimism.

Looking closely at the annotated image here I may have caught a nearby Quasar at mag 19.6. There is a dot in just the right place but I can't be certain it's not noise, I'll check the full size image when I get home. The link claims it is 8 billion light years away.

I've been reading up on the dwarf, Walter Baade used the 200" Hale telescope to establish its distance. Its RR Lyrae variables are at about mag 20.5.