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Hi Still a little overdone perhaps. eos600d? So as a starting point maybe try: RAW, ISO800, 5s, f8, no drizzle; leave the aperture wide open and place a M6 washer over the front of the lens. Cheers and HTH

Excellent image. Loadsa detail you don't usually see. I'm absolutely useless with colour, but had a go HOO. It may help in controlling the red a little. Cheers **@stu: have you had a go at this with the same filter on your f4? Should be an interesting comparison.

Yes. My bad. I read that the 8" was f5 and the 12" f6. f5 is offset. f6 is much more central. But the method I gave to adjust the secondary is still correct; the secondary is both too far toward the primary and is rotated incorrectly. Cheers

Hi The main difference between f5 and f6 is that for the latter, you'll find the primary donut reflection will collimate almost centrally, with very little offset. You have it set (perhaps by habit?) more as if it were at f5. Primary visibility is not helped by the small secondaries fitted to sw Dobsonians. The fix is easy: 1. Move the secondary toward the open end of the tube a few mm. To do this, loosen the three secondary adjusters and turn the central screw clockwise. 2. With the secondary adjustment screws still loose, rotate the secondary until it appears circular. Relative to your photos, you'll need to rotate the secondary anti-clockwise. Repeat 1 and 2 until you can see the missing primary mirror clip. Now you will be able to complete the collimation Focuser? Be sure to read the common collimation myths and Seronik's no nonsense collimation guide. Note that the fast and slow photographs in the AstroBaby guide are incorectly labelled. They should be like this (you're aiming for the slow version): fast: slow: Cheers and HTH

Therefore, and as your images show, apart from tilt, you are too close. Can't recall exactly but we needed at least 58mm from the shoulder of the m48 thread. The m48 t-ring alone will give you 55mm. With your 2mm spacers that's probably around 57mm, but you're now at the safe thread limit. Baader give 57.5mm. Use 58mm as a starting point. The low profile t-adapter with a set of extension rings makes this easy. It removes the coma, but introduces astigmatism. If you want out-of-the-box-corner-to-corner over aps-c, perhaps consider the GPU. Cheers and HTH

Hi If you're able to reach focus with the clicklock, then it looks just about as good as you're gonna get. If not, use a low profile eos-m48 adapter and a 12mm extension tube. The tilt was measured using Siril under Ubuntu 22.04.3. The same version will run under Mint but if you're interested in the journey as much as the destination, you may wish to build the latest version from source. Testing and reporting bugs helps the developers toward the next release. HTH

Hi Excellent shots, but if you feel you want to take it further... Both images are tilted; make sure that the primary mirror is adjusted correctly and ensure that the camera-cc assembly be inserted correctly into the focuser. Baader cc? Lose the m42 adapter and go with 58mm from the m48 shoulder. If your focuser has a compression ring, avoid clamping across the shoulder of the undercut of the cc. Or just remove the compression ring. Simply dismantling and re-seating usually helps. But hey, 450d on a 200 f5; if you're satisfied with the images perhaps stay as you are. Cheers and HTH

Hi Nice shot. I removed the gradient and gave it a crude stretch. There is colour:) As you can see, I'm hopeless at balancing it but I'm sure one of the processing gurus will be along soon. Cheers and HTH

Hi. What's wrong with it? What are you expecting over and above that which the 150 offers? Cheers

For astro imaging, along with logical thought, any remaining sanity you may posses is a distinct disadvantage.

https://linuxcb.blogspot.com/2023/09/siril-dslr-processing.html HTH

Hi T7, so lose both the dark and in-camera bias frames. Instead, simply subtract the offset before stacking. That should clean things up considerably. Cheers and HTH

Absolutely. I got nowhere following the rules!

Hi We had similar row with a 700d. Someone then dropped it, after which the line disappeared. Whilst we don't recommend the gravity method, a sharp nudge in a warm room may help. Otherwise, just work around it in software. Rather than resort to dark frames -which will introduce further artefacts- simply run the sequence via Siril's banding algorithm before registration. Or even easier, on the end result: Cheers and HTH

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Very nice. I've a feeling though that there's far more information in the image just begging to come through; go easy on where you think the black should be: Go for something more like this perhaps: Cheers and HTH

Hi You can't control the sensor temperature, so best to lose any type of dark frame. Try without? Instead, simply remove the bias. To lessen banding from light panel flicker, use an extra t-shirt and increase the brightness. Anything over 2s exposure should be fine. EKOS' flat frame wizard is your friend. HTH

Hi Nice image. A few bits we need: -power supply -light source for flat frames -exposure for flat frames. For now, simply run the whole pp sequence through Siril's vertical banding before registration. Cheers

Yeah. They use the f5 tube and relocate the focuser and secondary further toward the primary, but far too far, pushing the focus position around 180mm from the tube. Without being close to the aperture reinforcement, tightening the secondary spider to the point needed for collimation to hold, dents the tube. Unworkable IMHO. The 6" f4 is even worse. Just look where the tilt-inducing focal plane is situated:

Hi To help us, maybe post: - an uncropped frame - a frame of a bright out of focus star in the centre of the frame - a view in daylight -with the imaging camera removed- into the focuser - a view of the camera assembly fitted into the focuser - details of the optical train e.g. is there a coma corrector or filter Cheers

Hi 450d: offset 1024 We do not recommend using in-camera bias or dark frames with this camera; simply subtract the offset. Hence... ... perhaps best to learn to use Siril manually so that you are in control. You'll probably find manual usage is quicker anyway. You can use EKOS' flats planner to set the desired adu. Place sheets of paper between the telescope aperture and the light panel. To avoid introducing more artefacts, flat frames using a typical light panel need to be at least 1s duration. No theory here. Just hands on. Cheers and HTH

+1 The best advice we can give to anyone starting is to go along to an astro club and see the equipment first hand. Between them, the members will have experience of everything on your shortlist and will be only too pleased to show you the hardware, help you set it up and get you started. Cheers and HTH

Correct. But... ... at the same time, the pads do not allow the mirror to slip. They are soft(ish). They provide friction, unlike e.g. hard acrylic. The latter would allow the glass to slide easily. I think the idea is to allow for expansion and contraction of the glass with temperature, but prevent slipping as the telescope changes angle.

OK. Sorry. Take a ptfe pad and push it against a glass surface; it slides easily. Now take one of the mirror support pads and slide it against the same surface. There is much more resistance, as if it is tending to stick to the glass, but without actually sticking. Cheers

Hi everyone I need to replace the floating mirror support pads on an ES pn208. The type of material upon which the mirror rests is a bit like silicone sealant which has been allowed to set. It's quite firm but is able to hold the mirror with minimal slip. I've messaged Bresser but so far nada. Question. Does anyone know the material from which the pads are made and/or a possible source? TIA