alacant

Hi. I've an affordable refractor too and have managed to tame the CA [1]. The cure is a uv-ir cut filter -to help the inadequate in camera filter and prevent those wavelenhgths recording as visible- with deconvolution of the blue channel so as to push the blue back to the central star. The method is unfolding here... HTH. [1] Which IMHO is infinitely better than having hideous spikes protruding from every star!

Hi everyone. Short tube, big secondary and proper 2 1/2" r&p focuser; the new Bresser 150/750. Makes pds' look decidedly dated! Just add CC for instant AP.

Absolutely. The LRGB module will pull only the channel(s) you choose, be it separate files or a colour stack. HTH.

Hi. StarTools right? It looks like the blue has fattened the stars: Load the blue only in LRGB, Autodev. Decon, radius 3.0*, 1 iteration, show result. Restore to Linear Wiped Deconvolved. Save that as blue.tif. Now fire up LRGB again, load the Red and Green from the original but use your blue.tif for the blue. It concentrates whichever channel is 'fat' back to the central star. After killing tracking, Magic a pixel or two. HTH. *That's my starting point. YMMV

+1. Again and again: have a go with what you have. There's not enough experimentation. Things really have moved on from the EDsomething on an eq6 days. And IMHO for the better.

Hi everyone. I was fed up of galaxies being a small spec in the frame so I set up this old 6" refractor to have a go at Stephan's Quintet. Still quite small but at least identificable as galaxies this time. Despite many dismissing it out of hand, I think it worked quite well on my dslr. Having said that, when it was first made -in the mid 90s I think- I doubt whether this would have been possible without a house remortgage! Cheers and clear skies.

Hi. No expert but I believe it is because of the canon sensor recording invisible radiation as blue at one end of the spectrum and red at the other; it shouldn't. It's the same effect that makes the stars fat. A #8 reduces the blue and a #12 eliminates it, but I don't think that's what you're aiming for (?). HTH.

The semi-apo doesn't really do CA; I think it removes around 50%. A uv-ir plus a skyglow I find works better but still a great shot. HTH.

Hi. We've a thread on the StarTools forum. Basically we decon the blue channel back onto the central star then pull the RG separately on top of the de-convoluted blue. It sounds complicated but do it a few times and it becomes second nature. Helping the weak Canon uv-ir filter -it records them as visible- at source with a proper uv-ir block filter really helps too. If you just want a quick fix, put the fat stars in a mask and the hit filter > fringe killer. The problem with the latter is that the halos are still there, just in a shade of grey. But hey, it sure beats having spikes sticking out from every star! HTH.

...just the moon and skyglow then. No need to spend a fortune!

Here's a side by side. Both have moon and skyglow which removes the muddy orange. The better image is with the uv-ir I mentioned. Under €25 for both on AliExpress. HTH. **Taken on an eq so not strictly on topic but I thought my experiment findings -all by coincidence of choosing the wrong filter in the dark- may help other achro ap users. If you want to eliminate the ca completely you can use a 495nm long pass (wratten 12) along with the uv-ir -useful for e.g. the horsehead where there is a bright star in the fov.

Ah, I should add this filter (I think) is only true for dslrs, especially modified ones where the uv and ir record as blue and grey on the sensor. I believe ccd cameas work in a different way. I'm sure someone more techie could do an explanation...

Hi. I find modern achros good for AP. You may want to get one of these which prevents invisible radiation being recorded by the sensor. HTH.

Great thread. I don't have an eq3 -yet- but I shall be sticking around here for sure. Maybe we can pick up newcomers who've been given different -but of course in good faith- advice as to how to begin. I really wish that someone this time last year had advised me to get an eq3 for what I already had -my dslr- and have a go. Clear skies.

+1. Exactly. It would put anyone off. The advice is (at least) 10 years out of date. I think we should aim the level of posts at the level of the forum. The jargon is at times insurmountable. Just my €0.02.

Hi. Nice proposal. My (selfish) reason for being here is to have somewhere to discuss the experimental aspect of AP. Somewhere where we don't expect perfection. If we all stick with what the purists tell us we must all own APOs and those ritchey cretin -or whatever they're called- things and we never go anywhere new. This is the only place which has embraced anything experimental. So +1 for the proposal and thanks for taking the time to categorise it. Specifically I'd like to lose the alt-az only constraint; there are good cheap eqs too. So there's one fewer item to the all embracing concern. May I propose simply 'ap on a budget'? Or, dare I,;'ap under €500' [hides] OK then, €1000. HTH.

Hi. I found by accident that this filter cut the blue halos almost to nothing. It's something to do with uv (or ir?) being recorded as visible by modified canon sensors- I'm sure someone with technical knowledge could explain far better and in more detail. I didn't post here because I used an eq mount but just to add support for creating a budget-have-a-go-with-what-you-have-doesn't-need-to-cost-a-fortune section, I think this is the sort of post which would fit in there. I'm gonna post the snaps here anyway in the knowledge I'm off topic for which I apologise in advance. HTH and clear skies.

+1. May that include achromatic refractors? So often rejected out of hand for imaging. They've come a long way since the rule book was written. Cheers and clear skies.

+1. Very well put. I'm all for having a go with whatever you have. A cheap telescope on a cheap mount is capable of far more now than 10 or so years ago. The telescopes are better for a start. It's great to see threads like this where we push the limits and experiment. Rules are there to be broken. I don't think its a coincidence that this not-an-ed80-on-a-heq5 thread is so popular!

Me too. I'm guessing a fork?

Hi. +1 for having a go with the big refractor, underrated I feel. These days better than they used to be. I've a f10 petzval working at f5. Loads of fast, affordable no-spikes flat field contrast. With a uv-ir filter it works well and a decon on the blue channel really nails it. Have a look at this ST thread for the workflow. HTH and clear skies. **having said that, to get the whole of M31 I think the biggest you can go on an aps sensor is a 300mm lens. Do maybe nearby m33 instead?

Hi. Nice images anyway. I think the main advantage of Ivo's ST layers is that you can choose how much of each exposure you take.

Hi. Process the 20s and 10s individually and then layer them in ST. It's just a couple of clicks. HTH.

Hi. Good suggestions but I think you're gonna have to wait until next week for the nebulae. HTH.

Could be worse; new moon. Pass the scotch...