Stub Mandrel

I always take the cover off and leave the scope horizontal to cool.

I've just got one of these:

https://www.365astronomy.com/optolong-l-enhance-light-pollution-dual-bandpass-narrowband-imaging-filter-2.html

My DSLR is astro modified so I have high hopes, but they are supposed to work well with unmodified DSLRs under light pollution.

I have often wondered how effective visual filters are, I imagine they work but just not as dramatically - and considering how well a £10 moon and skyglow filter improved my images I don't have any preconceptions that cheap filters aren't worth trying.

I'm, waiting for the next clear night, but here's a review:

https://astrobackyard.com/optolong-l-enhance-filter/

37 minutes ago, Gina said:

Brought the imaging rig indoors in a gap in the rain ready to swap to the 135mm lens and make new camera mounting brackets that will allow the camera to be rotated.  Currently printing the 135mm lens focus gear.

I'm printing the last bit of my cooled mono cam. I thought about what I'm doing and how easy it's been with a 3D printer and I'm tickled pink. This would have been a major undertaking without the printer and despite being printed from plastic, accuracy is assured as the sensor mounting points and camera adaptor mount are concentric and parallel by design and nothing else is critical. Can't wait to use it!

9 hours ago, symmetal said:

The green graph line is the subs ordered by quality from left to right, left being the best. The green line quickly falls from max quality to a lower quality value and then decreases more slowly across the graph before quickly dropping to very bad quality at the right hand side.

It's not always 'very bad' at bottom right.

Top left is the 'best image'  - sometimes AS3! can assign high quality to really bad images which have strong artefacts, using PIPP to get rid of the 5% worst images can help eliminate these.

Bottom right is the 'worst' image. But if all the images are 'good' the graph will still drop to zero at bottom right. As an example I took 50 stills of the moon the other evening with a dslr on my scope. At 1/400 (2.5ms and through a Ha filter) the subs were virtually indistinguishable and any of them would have been usable but AS3! still ordered them and graped from top left to bottom right.

This is why you shoudl always use the slider to check what the graph is telling you. usually you will see poor subs at one end and better at the other with a 'break' in the curve that helsp you find where the quality changes. This can be a very obvious step if cloud comes in!

This is that moon, 100% of frames stacked:

10 hours ago, Merlin66 said:

OT.

Neil,

Can you help me understand the use of the green cursor in the AS3! quality graph?

Sure, you can move it across the graph but it doesn't automatically pick up that point for stacking etc?

Is there something I'm missing?????
 

It shows where the image being previewed is in the quality ranks.

12 hours ago, dyfiastro said:

I live just north in Ynyslas,

You luck b***r.

My first job was hacking down rhododendrons at Ynys-Hir. I bet tehy are still there...

HI David,

That's not bad at all for an unmodded 1100D. Main improvement would be to experiment with curves and gamma to bring our more of the background nebulosity:

Next step up is removing the blue-green filter to make the camera more sensitive to Ha.

If you save your image as a PNG file it will display in the forum as a more quickly displayed [review (and folks can right click it to see the full image).

Lovely report Rob!

How you manage to do this AND image as well is beyond me 🙂

It's interesting. I decided to go for a refractor, in the end I made a 66-400 using a Skywatcher 66 ED lens cell. Quite small and slower (f6 compared to F4.5) than the 130P-DS.

It has a different FOV and does give lovely results, but aside from the FOV and star spikes there's little difference, plus I only collimate the 130P-DS about twice a year, it just doesn't go out of collimation.

So my advice is get something of significantly longer or shorter focal length, the 80ED at 600mm is virtually identical to the 130P-DS at 590mm, and a much slower scope. So you are spending a lot of cash but not actually adding any options to your armoury and increasing the exposure time.

2 hours ago, Rusted said:

So did I. But I was told off by somebody here.

Well I tell you 🙂 - (1) look at the quality graph in Autostakkert, there's often an obvious cutoff point. (2) use the slider and see where the sub quality starts to decay. (3) stack different percentages. If you get an improvement, try going a bit furtehr in that direction, if it gets worse head the other way.

As you increase the number of subs noise decreases but at a critical point the image starts to 'soften' as you add in poorer subs, it can take several  runs to find the sweet spot and its not always teh same.

I don't think I've ever gone below 5%, with too few subs, however good they are, there's too much noise.

I think it's the distance between the end of the focuser tube and the focus point, so you have up to 75mm for any filters, flatteners etc, plus your camera will probably need some of that distance -  a typical DSLR takes a whopping 55m.

A few pics. the lids for the electronics and the dessicant are  printed 0.2mm under nominal size and 'click' in with the surface texture. I may fit an internal holder for a 1.25" filter, to create a smaller sealed chamber for the dessicant.

The sensor already has a small rectangle of heatsink putty on it which connected it to a stalk inside the case.

I've fitted a cooler to a Touptec Mono, take a look at this post to see the difference cooling makes to a 10-minute dark sub:

Success, I just took two 10 minute subs. Both in my 'office' where the temperature is currently 25 degrees, thanks to computer and busy 3D printer. Here is the dark taken before connecting the cooler, and the dark taken afterwards... Both 600-second PNG captures out of Sharpcap with no processing. Can you guess which is which 🙂

The 10 minute cooled sub is indistinguishable from a 2-second one.

and CED 214:

CED-214.FTS

Oh lordy!

I have discovered I was 'applying adjustments' to the FITS in DSS. As it was the default curve  with the data down near the left teh dark bits were being comressed, so little noise byt 'quantisation' = "posterisation".

So I'm reprocessing, the result is nosier backgrounds, but a much more natural appearance:

Here's a proper FITS:

SH2-86.FTS

For some reason I'm now getting a dark strip top and bottom, so I'm cropping those out.

Important to reset FITS liberator after loading a new image - I still don't have a clue how it works...

Here's a new CED-214:

And SH2-86:

41 minutes ago, tooth_dr said:

Would you mind posting the unprocessed fits? Id like to try processing the top one if that’s ok!

I'm glad you asked - it's made me check and I've discovered I've been saving the FITS with the default DSS curve applied. This is compressing the dark part of the image, hence the posterisation!

I'm running through some quick reprocessing then I'll try and upload a FITS or two.

3 hours ago, Thor92 said:

 Any suggestions for any other deep sky objects that should be relatively 'easy' to find?

J

M57

M27

Plieades (early morning)

Most bright globular clusters M13, M2.

5 hours ago, Spacehead said:

The thing is that I write websites for a living - and nobody pays me - the most i get is £150 for two weeks solid work.
In other words im skint as - so guiding is out of the question.
 

Guiding doesn't demand quality optics or super expensive cameras.

I assume you have a laptop then.

Get a cheapest astro cam off the web, cheapest you can find that will do 2 or 3 second exposures - do avoid the 'planetary only' ones. Or look for a used one on the classifieds here.

Combine this with a 0.965" adaptor and the cheapest toy telescope off e bay and you are good to go.

These are two images from last 20 September, again 5-minute subs using my cooled 450D with the 130P-DS and a 7nmn Ha filter. They have been stretched in FITS Liberator and very lightly adjusted in photoshop, with noise removal in Astra Image. again the challenge is 'posterisation', so the darkest areas have been masked out and blurred a little to make the transitions less harsh.

SH2-86 - the 'Poor Man's Pillars of Creation'

CED-214

Actually an L-Enhance (tri-band DSLR) filter not another Ha despite what it says in the photo!

Hi @Spacehead,

I'm afraid it's really unlikely the bearings are at fault - the play should be removed by adjusting the preload on the bearings carefully.

The errors are inevitable, most come from periodic error on the worm, but every gear in the drive will introduce some error. Even belt drive has errors due to imperfections in the pulleys.

They will get worse over time, not necessarily wear but  gears and bearings will gradually shift under the influence of cycles of heat and cold, slowly increasing backlash or causing binding.

That's why the very best mounts use plain spindles bearing on smooth discs and optical encoders (which can be made far more accurate than gears as they bear no loads).

When you consider that tracking with typical accuracy of 1 arc minute is the equivalent of firing bullets through the earth at Australia and getting every one of them to hit a target the size of an olympic swimming pool.

When I do my planetary imaging, I see a shift of several pixels just from me shifting my weight from one foot to the other near a tripod leg. Just picking my camera  timer up can cause a brief execursion of several arc-minutes when imaging.

The mass of a telescope is enough to cause variations over time.

So, the sort of variations you are seeing are inevitable in any mechanical mount affordable to mortals, yet it can be effectively eliminated by good guiding which uses feedback to keep the errors to about a scale of 1 pixel.

I used to get reliable 30-second subs, I could even keep most of them with up to 2-minute exposures.

Then I started guiding.

Then I discovered I had to put some more effort into removing backlash etc.

Now I can guide to pixel-accuracy for 5-10 minutes for every sub (if the sky stays clear!) But if I lose my guide star, most of my subs will have eggy or double stars.

Hi Thor your moon is nice.

You do know that andromeda is much bigger than the moon? You could be looking straight through it...

Now the moon is moving away from it you should be able to see it in your finder scope.

Get Mirach in the finder (easy to do) move up one noticeable star.

Now move up the same amount, it should be in the centre of the finder, at the apex of a triangle formed by two slightly fainter stars.

You can find it this way with the naked eye.