The Pinwheel Galaxy

[Graeme]

Last night I set up to capture an image of Messier 101, the Pinwheel Galaxy. The plan was 9 x 420 second exposures but it clouded over after 4!



https://1drv.ms/u/s!AtzUKEWck9gpvvc01AZ ... w?e=dvaBsi

Regards

Graeme

[HansV]

That's wonderful!

[stuck]

Last night I set up to capture an image of Messier 101...

Impressive I've often admired astrophotos but I've never tried it. Please can you give details of your set up? Camera body & lens, focal length of lens, f stop and what software you used to stack the (only) 4 (instead of 9) images.

Thanks,

Ken

[Nick Vittum]

Excellent! Thank you for sharing.

[BobH]

Beautiful! Well done, Graeme!!!

[StuartR]

Lovely. I too would like to know about the camera and seetup

[Graeme]

I've often admired astrophotos but I've never tried it. Please can you give details of your set up? Camera body & lens, focal length of lens, f stop and what software you used to stack the (only) 4 (instead of 9) images.

Could I? I would love to! In fact I could bang on about it all day! It's really nice to be asked.

Thanks all for the interest.

My telescope is a Celestron 9.25" f10 2350mm focal length SCT. It sits on top of a Celestron CGX mount. The camera is a Canon 600D mounted directly on the back of the telescope. This gives me a field of view of 30'x20'. I have an 80mm refractor guide scope that sits on top of the main telescope.

I control the telescope from the garage pc using USB cables. The telescope and focuser are controlled using the Celestron CPWI software and ASCOM drivers. Images are captured using Astrophotography Tool software (APT) which controls the camera and the mount once it is set up and aligned. It also outputs to Stellarium. The guide scope camera is controlled by PHD2 software (Push Here Dummy!)

APT captures Light frames, Dark frames, Bias frames and Flat frames. DSS (Deep Sky Stacker) stacks all the data and takes care of calibrating the Light frames with the Darks, Bias and Flats. Then finally I take the DSS output file into GIMP (Graphical Image Manipulation Programme) for processing.

The next step for me is a dedicated astro camera but I need to master the DSLR a little more fully first. (And save some money!)

It's a constant frustrating learning curve, but I love it! And if you're really interested I would recommend a visit to here: theskysearchers.com

My gallery is here: https://theskysearchers.com/app.php/gallery/album/130

Regards

Graeme

[stuck]

...My telescope...

Ah! OK, 'proper' astro kit
That explains this image and why the images in your gallery are so good

I have a higher spec. camera body than you (mine's a Canon 90D) but I don't have a telescope or the means to track star movement and my telephoto zoom is not an L series lens so these sort of images are beyond me. Unless the stacking software can automatically align images that 'creep' due to the the earth's rotation. If it can then I suppose I could try stacking a huge number of ~30 second exposures.

Meanwhile, one more question for you. The images that APT captures, are they effectively the JPEGs that the camera produces or does it work with the RAW files? I ask because I guess a real problem with this sort of photography is noise. The in-camera JPEG conversion won't do a very good job of removing noise and any decent RAW converter will do better. Arguably the best is the PRIME noise reduction option within DxO's Photolab but it only works on RAW files.

Ken

[Graeme]

Thanks for your kind words but my images don't come close to the monochrome camera narrow band filter people!

Your Canon 90D would capture some lovely astro images with it's 32M pixel sensor. I'm afraid the DSS stacking software is not able to correct star trailing to compensate for the earth's movement. There is a programme that can de-rotate a video of Jupiter (10 hour day) to stabilise an image, so you might think it would be possible! There is a rule of thumb that says 500/focal length will give you a maximum shutter speed to avoid star trailing, so a 50mm lens will give you a 10 second exposure.

APT is brilliant! It will control all the settings of a DSLR so it can capture JPGs or the Canon CR2 RAW files, but as you say JPGs would be hopelessly noisy. DSS calibrates the data files with dark frames (sensor noise and hot pixels) and bias frames (the electrons present on the sensor pixels before the photons arrive) and these are taken with the telescope covered up to capture the just the noise. Then the noise is subtracted from the data files. DSS outputs a TIFF file or a FIT file and GIMP is used to process the image. The processing can take as long as the capturing!

It's a great hobby!

Regards

Graeme

[Rudi]

Well done. Very impressive.

[Graeme]

Thanks Rudi.

[stuck]

...stacking software is not able to correct star trailing...

Pity.

...rule of thumb that says 500/focal length will give you a maximum shutter speed to avoid star trailing

Where, presumably, the focal length is expressed in terms of a full frame/35mm sensor? Thus for my telephoto zoom at 250 mm, which equates to (250x1.6) 400 mm on my 90D crop sensor, the max exposure time is 1.25 secs.

This might give me a GAS* attack.

Ken
*GAS = Gear Acquisition Syndrome

[Graeme]

Yes, that's a full frame camera sensor.

I can see evidence of GAS! You are infact teetering on the edge of a rabbit hole that is astrophotography. I have seen many people get sucked in. Be prepared to let it swallow you or walk away now!

Regards

Graeme

[stuck]

...the edge of a rabbit hole...

I think you meant to say 'black hole'

Ken

[Argus]

Beautiful, Graeme. Thanks for sharing.

I can see evidence of GAS! You are infact teetering on the edge of a rabbit hole that is astrophotography. I have seen many people get sucked in. Be prepared to let it swallow you or walk away now!

To help Ken get a bit closer to the rabbit hole, as if that was needed, some inspiration photos from a blog I think I have mentioned once or twice (when he got a photo posted on NASA's APOD blog), Clear Skies. (There are of course a very large number of sites and blogs covering astrophoto.)
https://klarhimmel.blogspot.com/2017/03 ... abbey.html

I was thinking about this earlier, is it difficult to track (if that is desired) without a tracking mount etc. to adjust manually, reposition, or is it something that advanced stacking software etc. can help with?

[stuck]

To help Ken get a bit closer to the rabbit hole

It's OK, my GAS passed when I Googled Graeme's kit and saw the cost

Ken

[Graeme]

I was thinking about this earlier, is it difficult to track (if that is desired) without a tracking mount etc. to adjust manually, reposition, or is it something that advanced stacking software etc. can help with?

Thanks for the blog link Argus.

You would need a fine steady hand to track manually. I'm not sure it's feasible. And I'm not aware of any stacking software that does it. Although DSS can track a comet moving through a field of stars. So if you know any good programmers perhaps we should have a word! For anything more than 30 - 40 seconds, depending on focal length, a guide telescope is a must. It's not possible to get a polar alignment accurate enough for longer exposures.

Regards

Graeme

[Graeme]

To help Ken get a bit closer to the rabbit hole

It's OK, my GAS passed when I Googled Graeme's kit and saw the cost

Ken

Yes and in the rabbit hole there are many shiny things!

I have been fortunate to have left school and worked for the same company since 1974 and I started a final salary pension scheme when I was 20. So it did cost a few bob but I saved for 40 years for it! Anyway the cost of the telescope is nothing compared to selling up and moving to a dark place in the country to use it!

Regards

Graeme

[stuck]

...a dark place in the country...

I am very fortunate that I'm less than an hour's drive from here:
    https://www.forestryengland.uk/dalby-fo ... lby-forest

Naturally that means in the 20 years I've lived in this area I've never actually been there at night.

What's that funny noise? It must be Greame grinding his teeth at the thought of such a waste

Ken

[Graeme]

Unbelievable!

I know what you mean though, having lived near Rochester Castle and Chatham Dockyard for 20 years, I hear they're both hugely interesting, I've never been to see either!

Regards

Graeme