alacant

Hi Nice. Fast and furious. Look no further:)

Does the cc have an undercut?

What is unacceptable for some of us, may well be ok for others. We may have a bad batch of the lens for example. Best to try it first, no? Cheers

Mmm... Hi I hope it turns out similarly for you, but perhaps more realistically: Cheers

Which also needs a third screw tapping. Compression rings with the Baader cc undercut are bad news. So that the compression ring fits fully in the cc groove, lose the M42 adapter and attach the cc directly via its m48 thread. Or, better, as @Heizelsuggests, go back to the original collar and tap a third screw there instead. Cheers and HTH

Hi Unless you're after strict scientific accuracy, there is a good alternative. We tried the optolong offerings and found we got similar results using a €30 UHC. Similar effects. Different marketing. And yes, you can split colours and do HOO stuff too. As with optolongs however, the UHC still blocks most of the spectrum, so there's no free lunch; you still need long exposures to get anywhere near. Worth considering? Cheers and HTH

Hi I believe it fair to say that the 75-300 zoom is not perhaps the best lens Canon have ever made;) You may just be ok at 135mm or less but you're gonna need f8 at the fastest. Wide open it's, well... You get the idea. An old eBay Zeiss or Takumar 135mm or 200mm along with an eos adapter will give you a much better chance of getting something decent without breaking the budget. But hey, try it. Maybe come back to the filter question when you've tried without. Star Adventurer? Great idea. Just use a decent tripod. Cheers and HTH

Until you can confirm, maybe...

The best way of finding out would be to try one at an astro club.

Hi The reduction to 1.25" Use 2"/m48 connections throughout, a field flattener and take flat frames. Cheers

Hi Yes. No problem. We restored an old 250p. It goes fine on an -even older- eq6. With the lighter pds and a modern eq6 you're in for a pleasant surprise. You really do notice the speed of the thing. Try side by side with a 150mm;) We'd still recommend however spreading the tube rings on a long losmandy plate, a rigid rail to tie the same along the top, uprated springs, sealing the mirror to the cell, a dew shield, a black shower cap and an oag. It sounds a lot, but it's only around an hour's job. Cheers and HTH

Absolutely. We've probably never had one that far misaligned; the tilt on the secondary has taken care of any non orthogonality. Cheers

Mmm... have a look at seronik and telia's collimation myths.

It could be. At this stage, we don't know. Not necessarily. Please see the links I posted. The OP has a Newtonian. The advantage you have with the rc is that you don't need to introduce any more glass in the form of a cc. The adjustments on a rc are tiny in comparison to the equivalents on a Newtonian and yes, more iterations are required. For your rc, maybe start a new thread? The differences are significant enough to cause confusion. Cheers

The Baader m42 adapter is known to cause tilt, in exactly the way you describe when you insert the cc into the optical train The m48 connection is directly to the corrector. Are you on zwo? Don't they include a proper m42-m48 in the box? Yes. If the compression ring fits entirely into the channel, then no problem. The issue is only when the compression ring is tightened part way between the channel and the full diameter. To eliminate tilt. I'll attach the Baader spacing recommendation. It has helped many a Baader cc user who has passed by here. I can't remember whether is has flexible rubber within. The skywatcher focuser e.g. does. Again, tilt inducing. HTH

Hi With the mpcc III and Baader's t2 adapter, I'm not at all surprised. Go with the m48 threads instead. Don't forget that you'll now need around 58mm shoulder of m48 thread to camera sensor. The other main issue with the mpcc is the undercut. The compression ring on the focuser will force it to tilt no matter how carefully you tighten around it. So lose the brass ring and have the screws bear directly against it. Or arrange that the imaging train clamps against a matt (or shiny type which has been sanded) m48 extension tube. You might also check the seating of the focuser. I think the GSO models are free of distort-under-load rubber, but it could be that the tension screw may need a 1/4 turn clockwise. then leave it. Use only the locking screw in the field. So that collimation holds at all angles, seal the main mirror to its cell, fit uprated springs, spread the tube rings on a Losmandy dovetail and tie the top of the rings with rigid aluminium profile. You may want to consider a Cheshire sight tube with crosshairs for collimation. Cheers and HTH **EDIT: forgot. Loosen the retaining rings for each of the cc elements in turn and on a flat surface, shake/nudge to seat them. Tighten until the ring just touches the glass; no more rattle can be heard. And of course, be sure to read both seronik and telia's collimation myths;)

Nice. @OP: you could apply that to the linear image, then process. It should really shine.

Hi Lovely shot. Minor improvements which are easy to do... 1. 80d: ISO 200. 100 may be even better. 2. Use flat frames: Without removing the camera, set the 80d on Av and point the telescope at an evenly lit light source so as to give an exposure of around 2s. Use distance/paper/card/t-shirts to control the light. Switch back to M and set the same exposure. Take at least 15 frames. 3. IIRC, to control the halos on a wo, focus on a white star using a bm. remove the latter then ease focus away from that point until the blue halo begins to turn red. Now compromise between those two focus positions. 4. Use a field flattener +1. Cheers and HTH

Hi I don't think we have a fixed answer, rather the use of an OAG is determined by the combination of mount, camera and telescope you have. With a refractor at 800mm, I'm sure you're gonna be OK with a separate guide telescope. But, if you're near weight limit on your mount, then go with an OAG. A properly mounted guide telescope wiil add around (at least?) 1.0 kg to your telescope, an OAG around 0.3 kg. We prefer OAGs for most telescopes; they're lighter and not only give nice stars, they give nice stars for every frame. even the one on the other side of the meridian flip, and even when using an out-of-the-box-low-end Newtonian. Having had to sort out many problematic guiding setups with separate guide telescopes, most if not all could be improved by mounting the guide telescope adequately. Preferably directly bolted onto a rigid rail joining the top of conventional tube rings. +1. To which we would add that modern astro processing software is also capable of rescuing images which in the past would have been discarded. Cheers and HTH

Hi everyone This is with the cheepo no-name cc which gives ~585mm. Not nearly as good as the gpu, but gives the wider field which just manages to squeeze these four into the frame. Thanks for looking and do post your 130-dslr galaxies. 700d @ ISO800 siril 1.0.0 startools 1.8.525

Hi Recommendation: remove both the baffle and the clips. Seal the mirror with three generous helpings of neutral silicone sealant to coincide with Skywatcher's cork. Problem gone Although I must say that your stars are certainly on the social-media side of scientific, verging on the artistic even. Post it on Instagram? It could catch on:) Cheers and HTH

Ah, OK. I think you may have misunderstood. You bring them along with you. I've never yet met an accountant who would say no to a weekend away, Especially on the promise of sun, sea and sangría;)

A weekend around new moon perhaps? Not sure where you are, but air travel is affordable ATM. Dublin and Amsterdam come to mind ~€100 i/v including checked in telescope.

They introduce artefacts and noise patterns which make processing more difficult. Amongst other problems in their use, it impossible to fulfill the main requirement for dark frame subtraction, that of temperature matching. If you really must use them, there are algorithms which attempt to reverse the mismatch. But best to simply avoid. Best to dither between frames and stack with a clipping algorithm. Siril is the best we've found for this. HTH

Hi Lovely shot. 80D? So ISO 200 and lose the dark frames. Cheers and HTH