Astrophotography – equipment

Filtering the Crescent

Over the last couple of weeks I’ve been imaging the Crescent using different focal lengths and filters

Widefield 135mm

I was working out that this is the fourth time I’ve been imaging in or around the Sadr nebula. On this occasion it was because I’d already started on the data for 900mm shots of the Crescent and I thought it’d be nice to have a wider shot of the general area, putting it into context. I was inspired by Neil’s recent results with his Triband filter to see if the same (or similar) technology in a clip filter would help with wide frame nebula images and acquired a Skytech Quadband (that transmits 2 35nm bands around Ha, Hb, Oiii and Sii – hence the name) . I must say I’m quite impressed- I got this from a sequence of 20x 150 second captures on Sunday night under a 99% moon using the Russian made 135mm vintage lens I’ve posted about previously. Normally I’d only attempt proper Narrowband under these sorts of conditions, but I thought it coped pretty well under the strong moonlight. The only slight concern is the halo around Sadr itself.

The photo picks out how prominent the Crescent is (below and to the right in this picture), but also shows how “busy” this bit of sky is- the Butterfly nebula pops out, with its prominent dark lane, but the fainter cloud that it’s a part of extends beyond the frame. There are also clusters aplenty- my favourite is M29 – the Space Invader cluster just below and to the left of the centre. Probably my eighties upbringing…

Hydrogen Alpha

These are taken using a Baader 7nm Ha Filter on a modded Canon 550d in a Skywatcher 200p- altogether I got 12 10 minute subs before clouds stopped me. I think this is the best of the shots for showing the structure of the object and the shockwaves that form its shape; the monochrome also highlights the cloud of the larger surrounding nebula.

Oiii

This came from the same setup and 10 more subs, this time with an 8.5nm Oiii filter, and a 99% moon on 13th October. The only Oiii visible in this shot is around the nebula itself. The signal was quite a bit weaker than the Ha; this picture was created by discarding the Red Channel and then combining equally the Blue and Green using Pixelmath in Pixinsight.

Bi-Colour

Finally, it’s all brought together using the same process- this time feeding the Hydrogen into the Red channel and the Oxygen into the Blue and Green. I spent quite a bit of time playing with this one. Just feeding the data in, the red was total dominant and I progressively multiplied the Blue and Green until it was more prominent (the eventual multiplier used was 2). I also experimented with trying to change the balance to bring a little more colour into it, but that also artificially unbalanced the star colour so I decided to leave it even, which makes the Oxygen mostly white when combining with the Hydrogen.

I’ve really enjoyed taking these different views of the same object and learning about it. The nebula itself, 5,000 light years away, is 25 light years across and is caused by fast stellar winds erupting from the Wolf-Rayet star visible at the centre of the nebula. It’s thought the star will imminently (in astronomical terms) become a supernova.

20/9/19 Part 2 – Imaging

Here are my images from Friday night. First up is my effort on Roger’s Hickson Challenge using an 8 inch scope and cooled 550d. In this frame are the 2 clusters from Pegasus- the Deer Lick group and Stephan’s Quintet. Guiding was really ropey whilst I was doing this (it was a bit breezy) and I had to abandon about a third of the subs- so this is 90 minutes worth of 4 minute subs:

This is a crop with the Deer Lick group:

And here’s Stephan’s Quintet. I’ve had a bit of an obsession with this object. I’ve tried and failed to observe it at least half a dozen times- it just seems to be right on the edge of what the 14inch can grasp. Looking at these photos I can see why- the camera really hasn’t been able to put much shape or definition on them:

This shot took until 11:45pm- when the mount was coming up to the Meridian.

Rather than continue to gather data I moved across onto the Eastern Veil. I really love observing this object- but this is the first time I’ve tried to image any of it- this is 32 4 minute subs. Quite pleased with the outcome:

Finally, I’ve been ebay-ing again and have picked up another vintage Russian lens- 300mm this time. See picture below- it’s not lightweight!!! I’ve found that using this one is much more like using a telescope: it’s harder to aim, it needs a counterweight and was too heavy for a ball mount, so I had to fix it onto the SA and therefore can’t rotate the camera at all (unless I start trying to engineer something myself). I have to say, though, for anyone wanting to experiment with wider fields of view- these old prime lenses are pretty good- and compared with other astro gear quite cheap. I think this is the longest focal length I’d try- I was initially doing 2 minute subs but was getting some trailing so dropped to 1 min 20. I could (and may) add guiding- but at the moment I want to keep it simple. This is 17x 2 min subs and 80x 1 min 20 subs (I just left it running whilst I was observing) on the North American and Pelican nebulae.

 

 

 

 

Weekend Opportunism

Between a busy work week, family commitments and some so-so forecasts it wasn’t looking good for astronomy this weekend, but it turned out pretty well.

Friday Night:
Imaging-
Didn’t get out until about 10:30 but tried to make up for lost time by setting both the main scope going and trying out my 50mm lens on the Star Adventurer. I had high hopes for the 50mm lens- it’s another oldie (I’ve had it about 15 years), but online quite a few people are getting great results with them. Well- I’m not in that club (yet). The diaphragm only has five blades and although I stopped it down to f2.8 (it’ll open up to f1.8) all of my stars are pentagons and DSS is refusing to recognise them as stars- so no results from that. Fortunately, the main rig saved the day: I went for NGC6946 – The Fireworks Galaxy with my 200p. Throughout the session low clouds were interrupting the view, and around half the subs were lost, but the ones I did hang onto gave the result below. Over the summer I’ve picked up a second hand Canon 550d that has been home modified with a Peltier cooler and put into a metal case- it’s not pretty, but it seems to be effective. This is 13×4 minute subs and throughout this session it held the temperature down to around 7-8 degrees which I’m pleased with (a couple of degrees below ambient, my 600d usually runs about 10 degrees above ambient and is consequently much noisier). The target itself is quite a bit smaller than I’d anticipated- this is a crop of about 20% of the frame. Despite the small size- I think this is a lovely target- both for its colours and the asymmetry in the arms.

Observing-

Whilst the cameras were doing their stuff I had the Dob out on the following objects:

The Double-Double- I used Vega to get the finders lined up then dropped down to Epsilon Lyra to check out the seeing. It was a straightforward split, but I could see that the transparency was not great.

M13 & M92 – I often start with these and never get tired of them. In Binoviewers at about 260x they fill the field of view and appear 3 dimensional. For me these are the only types of objects that actually look better in the eyepiece than in a photo; I love the difference in their appearance- M13’s great with lots of features, but a bit of a mess with arms everywhere, whereas M92 is compact and very neat. Just wonderful.

The Veil – I was reading a thread on SGL recently which referenced a Sky and Telescope article on The Veil (https://www.skyandtelescope.com/astronomy-blogs/explore-night-bob-king/explore-veil-nebula/) . Using this as a guide, and with an Oiii filter a 30mm eyepiece (55x) and a coat over my head I managed to explore just about the whole thing. I’m a bit prone to hopping from object to object whilst observing, so it was great to really take my time in the tranquillity of the small hours and drink it all in with nothing but the odd clunk of a shutter release and that American woman with the nice voice who commentates on APT saying “Dithering started…” softly in the background. Ahhh… a very nice dither contemplating the remnants of a supernova.

I was on the Veil for over half an hour and loved every minute of it, but decided with to move on with the Oiii filter and go check out M27. This is normally not a problem, but by this point the transparency had deteriorated so much I was unable to hop to it. Altair was the only nearby star that was naked eye visible and despite several attempts I just couldn’t find the stars in the finder to hop up to M27. Reluctant to retire I switched up to the North East to check out M31 as the skies looked better in that direction. Before I could get to it a bank of cloud blotted it out. Time for bed…

Saturday:

I managed to pop out briefly whilst doing other things on Saturday evening and set the imaging rig running on M13. This was a bit of an experiment: I’ve imaged M13 before, but with my guide camera on a smaller scope using the short exposure method. Whilst I was quite pleased with those outcomes (see https://roslistonastronomy.uk/catching-up-on-images) , I wanted to see how it would look with more integration time and a DSLR chip. This is 22x 4 min subs plus calibration frames and I am really pleased with it. As a bonus for the last half-hour it was running I sat outside with Sam observing the sky primarily with Mark 1 eyeballs. After a while we were both able to pick out the Milky Way running up through Cassiopeia and Cygnus despite the local light pollution. A real pleasure!

Fun with my Bridge Camera

Some pics taken this evening with my Nikon P520, when I went out ‘bat hunting’ (NB all these images are cropped!):

Saturn single frame!
Jupiter Single Frame
Jupiter Single Frame – you can just see two bands!
Jupiter and Saturn
20 Jupiters and 30 Saturn images stacked out of 40 each, drizzled x3 to make them big enough to see!.
Sturgeon Moon Colour
And the Sturgeon Moon in Colour, stack of 10 frames.

T2 to 2″ adaptor

Hi Folks

After buying my nice new shiny UHC filter from Astrofest, when I got home I realised I hadn’t actually got any way of using it with my DSLR. If I attached it to my 2″ diagonal, I couldn’t get enough back-focus and if I connected the DSLR via a T2 adapter, I couldn’t connect the 2″ filter.

After a bit of digging, I found this T2 to 2″ adaptor on eBay for the princely sum of £4.99. It arrived in 12days from China:-

https://www.ebay.co.uk/itm/2-to-T2-Adapter-M48-0-75-With-Thread-Black-Aluminum-Alloy-High-Quality-Durable/143111007190?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

Here was my original DSLR to T2 to 2″ connection:-

 

Here’s the new version with the adaptor:-

I haven’t tried it yet but I can’t see why it shoudn’t work. I’ll let you know

 

My Astrofest shopping – 2″ UHC filter

Hi Folks
After hearing all the rave reviews about UHC filters I thought I’d buy one at Astrofest. I bought this one from 365Astronomy as their kit is usually good quality . Very reasonably priced at £52 (show price).
Here’s an interesting article on light pollution filters:-
See you on Friday

Flats light panel

Since I’m currently looking to change to a mono camera I thought it would be sensible to have a look at making the flats process easier.

I’ve seen a few posts over the years where people have produced a light panel and added A4 paper to the front giving a nice flat illuminated area.

I wanted to do something similar so I purchased a cheap LED panel on amazon and cut around the telescope circumference. I left the box around the panel and added Velcro to the inside to keep it flat against the outside. I also cut out the power inlet and on/off button.

Very pleased with the result ! I’ll keep it velcroed to the inside of the observatory.

Esprit 120

Esprit 120 Part 1

I decided to purchase this scope as it fits nicely in between the focal lengths of my other telescopes. I have read lots of reviews of the espirit range and quite honestly haven’t found any negativity at all. I purchased the scope from FLO and spent an extra little to have the scope optically bench tested. This will serve as an additional peace of mind and I’m really pleased I did so. 

On close inspection of the scope I can see this is a very high quality instrument with great attention to detail. 

It comes with all the connectors etc that you would require to start imaging right out of the box. I did purchase the field flattener at an additional cost as I plan to use it purely for imaging. If your doing visual astronomy the flattener isn’t required. I also received a m48 to canon adapter but not sure if this is normally included in uk sales or FLO just threw it in ? Either way very pleased ! 

The retractable dew shield is a great fit and works very well with the two screws to tighten over the tube. 

The focuser is of excellent quality and feels lovely to work it back and forth. The only other refractor I have is a takahashi Fsq 85 and I’d say this is of equal quality. The locking knob sits underneath the focuser. I wasn’t sure about the locking knob in the beginning as I’m used to using the screw type on the Fsq but this is growing on me and certainly locks things down tightly. 

I also like the camera orientation adjuster which enables you to quickly frame the object your imaging. Again slightly different to the Fsq but excellent. 

Visually the scope looks stunning with clean lines and I like the splash of green SkyWatcher have added to their scopes over recent months. 

The optics look awesome and I’m really looking forward to testing it out when the weather clears. I plan to use a full frame canon 6d to start with so this will be a real test of the scope/optics. Going by the look/feel of the scope I’m very confident it will pass with flying colours. 

Make no mistake this is a finely engineered scope, love it !