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Thinking: mirror not evenly seated. Did you replace the cardboard/cork support?

IMHO, that's the strongest item in your setup. We use them all the time with beginners and not so beginners alike. Rather than start with the telescope (that's gonna be difficult), why not have a go with just the camera and a lens? Try e.g. a whole constellation with the lens at around 50mm to get started. Optimum ISO:800. You can control exposures from a laptop with the software that came with the camera, or from your 'phone (there are loads of apps) using an OTG cable. Cheers good luck and HTH.

... explaining remote client- server to someone in London at 4 in the morning...

https://drive.google.com/file/d/17p-lULiGN4fQ_G0mU4rbs9SNs2Dt0P6q/view?usp=sharing Well tuned? I wish!

Hi Your image does show that focus maybe a little off. Our only recent hands on with a refractor was with a visitor's 72ed, which doesn't give best focus with a mask. His method seems to work well though; use the mask to get close, then a white star in live view. Refocus to get the tightest centre you can with minimal fringing. The mask spikes seem to register -in this case- the red and green, leaving an ugly blue halo. This can be minimised by compromise focusing. But focusing apart, we find that by far the biggest factor in getting decent stars is the atmospheric turbulence. Rare is it we get steady enough seeing to support 1000mm (is that around the same as your refractor?); maybe just twice a month. On other nights, either don't do globular clusters or use a smaller telescope on different targets; galaxies and milky way stuff seem far more forgiving at any focal length. StarTools is available free to try, but I certainly don't rate my -15 minutes or I get bored- processing skills. I think that if you have good data, any processing would work the same. Cheers

Hi If this is the one you have, it cuts both. It looks like you get only blue/green. Here's the graph, (from here). Cheers

Hi No, neither am I. No theory here, we thrive on pragmatism, so gonna go with your 30s idea. Thanks.

Hi everyone Never got to grips with these targets, but am determined to get something decent this time around. This was with a dose of StarTools' HDR 'Reveal' at around 3px. One spin-off was the control of the -usually fat- orange stars around the centre. Any dslr globular imagers, do share your technique. Thanks for looking and clear skies. 700d + gso203 19x4min @ ISO800 siril 1.1.0, startools 1.8.527-2

Thanks for the link. I used to think consistent collimation was something only achievable on high end telescopes. Don't be alarmed however. Silicone sealant is easy to cut with a craft knife blade and lifts cleanly from glass surfaces. Once every 10 or so years. Cheers

Hi Try as I may, I cannot reproduce the blotches. Please tell us your process. StarTools produces a file with the steps you took. This is just 5 minutes in StarTools-1.8.527-2 taking AutoDev throughout and remaining close to the default values. Focus: With low end refractors, focus using a mask, then looking at a white star in live view, adjust until the blue fringe begins to disappear but before it goes red. For expert help, I'd recommend the StarTools Forum. Cheers and HTH

Bottom of the range telescopes need a few modifications to bring them up to astrograph standard. The GSO mirror cell and floppy tube in particular need to be fixed before the thing will hold collimation. Here's hands on with a GSO 203 f5: seal the mirror to the cell using neutral silicone sealant to coincide with the GSO cork; lose the mirror clips. Leave the mirror to settle under gravity for 24 h. You are not aiming to glue the mirror to the cell. It must have a mm or so of silicone to allow for thermal. fit six 1.6mm wire springs. Three active and three passive, the latter over the locking screws. leave the latter loose; tightening them distorts the flimsy casting. spread the rings on a 500mm losmandy width dovetail plate. this prevents most of the tube flexure fit a light plastic secondary support. As if by magic, collimation is held at all tube angles. Between sessions even. Cheers and HTH

Hi everyone Weekend. We had a bunch of visitors with what our director rather un-lovingly calls 'portatas' (portable-potato) aka Skywatcher 72ed, satisfying the Spanish waiting lists after a crate made it through from China a few weeks ago. Having been disappointed with my previous attempt at this target with a sw130p, I figured that the only way to get more of the galaxies with even less aperture was with longer frames. So this is 10 minutes. Still disappointed, as the extra time seems to have done little for the volume of the galaxies, and it's noisy. Dunno... Anyway, if you've had a go at this with your dslr, do post your findings. Thanks for looking and clear skies. 700d + 72ed. 18x10m @ ISO800. siril 1.1.0 startools 1.8.527-2

Hi Ask on the 130 thread? We keep only stacked flat frames taken with modified pds'.

Both nice. Prefer 1 for 'phone viewing.

+1 We largely ignore the theory and post only that which hands on experience provides. Interesting though it may be for some, we thrive not on theory, nor on so called 'experts', but pragmatism. Experience also helps. For example, to date, the number of 130pds telescopes we've fixed is reaching double figures.

1200d? So before applying background extraction, you should first apply de-banding. BOTH whilst the image is still linear. Unless you have bad light pollution, you'll most likely find that you'll not need the extraction. HTH

This is why the flat frame changes as you rack the focuser in and out. I'd do that first before diagnosing further. The GPU works fine with the shortened tube. In fact the focus barrel coincides with the end of the cc. Cheers

here Apologies to those who attempted to follow the link.

So does the OP. We simplify that even further, without using camera-produced bias at all. The argument against dark-flat frames and for fixed bias value was introduced by @lock042 -who knows about this stuff- here. here Certainly with our dslrs it works well and produces clean images. Correct, and works for us. Have a look at removing a constant value as linked to above. @Bibabutzemann if you haven't already done so, cut 10mm from the focuser tube. Cheers

Hi My guess is that the focuser tube needs shortening and blackening to prevent it cutting the light cone. Otherwise as stray light must be coming from somewhere, you have to be systematic. Here are a few other ideas: Exposures... With a different camera 2" filter on the cc Without dew-shield Without mirror clips Without cc In daylight with both ends of the tube blocked with a black shower cap. From a session at a dark site With blackend secondary edges and spider. Or just accept it. Bottom of the range reflectors need a lot of attention to bring (them?) up to astrograph standard. Cheers and good luck.

Hi. Yes.

Mmm. If I calibrate with your dark-flat, it doesn't work very well. If I simply subtract a constant bias value, it works better. Certainly good enough to go on and process, especially as I just guessed a value. @lock042 -who knows about these things- confirms that flat-dark frames are a waste of time. You don't need them-. Have a look here. Ah, OK. A 200p. That could explain the unevenness. A black shower cap over the end of the tube would be a better idea than shiny reflective foil;) Have a look too at the focuser base curvature; it quite often does not match the radius of the tube. A long -at least 30cm- dew shield helps and finally, a felt covering over the focuser barrel where it enters the focuser mount should get rid of the last reflections. Is the inside of the tube evenly matt? Grease marks? Nuts which protrude inside blackened? Secondary mirrior edges black? Spider matt black? I'm assuming you've already eradicated any cc issues. Cheers and HTH

Hi Perfect? No, But acceptable. Are you sure it's not just a light pollution gradient bottom up?

Hi Easily within reach of modern colour cameras. He's an example taken with the same camera as the OP. Cheers

Yeah. That's €silly. Here's an alternative which will fit the t2 throat adapter on your 533. Or any astro club would lend you one. Cheers.