DaveS

Probably my 130 mm f/7 TS Photoline. By suitable choice of reducer / flattener and camera I could get semi wide-field and enough resolution for galaxies, though I still love my ODK. Of course the GTC would be quite nice, and might come on the market when the E-ELT comes online.

A tentative plan of campaign is to buy a set of Astronomik Deep Sky RGB filters, and add a L3 Luminance plus a H-alpha. Then consider new telescopes or cameras for next year.

Had a look at those links, very interesting, and in synch with what I had been thinking as another possibility.

Many thanks Vlaiv. Will have a closer look when I'm on the office computer. On my phone ATM.

Ah ha. Didn't know of anyone else who has one.

Seems like I'm going to be assimilated by the Borg. "Resistance is futile".

Many thanks for the alert Olly. Back from the dentist. He's found a molar that needs to come out. Got decay in the root under a crown. [A very bad removed word]

Thanks Vlaiv, some very good suggestions. Will have to print a holder for the filter as the lens has an odd 60mm Leica filter thread. A bit busy ATM (Getting ready for a trip to the dentist, urgh.

There's no nosepiece, and nowhere to put a filter ahead of the wheel. The least expensive option would be a set of filters with less extreme blue response.

Thanks Vlaiv. My thoughts on OSC was to get a roll off in the blue, like the colour film I guess the lens was computed for (This is the ASI 533) Combined with an Astronomik L3 ahead of it in the train to cut the deep blue and far red. I have also considered the Astronomik Deep Sky filter set, again with the L3 as Luminance. But I'm in no great hurry to spend my money so plenty of time to get things right.

Found this online Leitz Apo-Telyt-R

Thanks Adam. Still a lot to consider. I'm liking the ASI 533, just concerned about the pixel scale. The Askar FMA 230 is interesting, but unless they are using two different ED glasses it won't be corrected for 3 wavelengths. I may initially go with the OSC camera option, perhaps with an Astronomik L3 to cut the blue. Then consider a new imaging telescope later.

Well, partly a focus issue. As I was using a RDF for locating M31 I was reluctant to move to a bright star for focusing then try to relocate my target, so rather "fudged" the focus to a compromise between R,G, and B so I could run the whole sequence without interruption. However during the initial focusing I could see that the Bahtinov figure for the Blue filter was less well defined than the others, even at focus.

My widefield imaging train is afflicted with Blue Bloat. I was using my 180mm f/3.4 Leitz Apo-Telyt-R on a SA with ASI 183 MM and Baader LRGB filters (An early version with quite a deep blue cut off). Last week I was at an astro meet and was imaging M31, just an hour in each channel (Not enough, I know) The result is below. This isn't the first version, I have been through all kinds of evolutions but none are any better than this unfortunately Therefore I was thinking of solving the problem at source. My options appear to be 1) A more modern apo 'scope. The closest is one of the Borg 55FL f/3.6 versions. I have also considered the Tak 60 with reducer, which comes in at a similar price when everything is added up. there are also a couple of Askar offerings of unknown quality. 2) Move to an OSC camera, whose colour response will be closest to the colour film the lens was computed for. A couple of options come to mind, the colour version of the 183, or the ASI 533, just a little concerned about the sampling with such large pixels relative to the FL of the lens. Keep the 183 mono for NB. 3) A different set of filters, with a blue cut-off that isn't so extreme. The Astronomik Deep-Sky set with the L3 IR / UV cut filter might be a possibility. Does anyone have any thoughts on the above? Any other suggestions?

Don't fit into any of them as I'm a bit of an obsessive imager who likes to go deep, 20 to 30+ hours on a single target and pull out faint tidal tails. But don't consider myself an astronomer's astronomer as I don't do spectroscopy / radio astronomy.

I will add, if you haven't already get it, buy This book and read it through at least twice before spending anything more on AP kit.

If you want fast, for something less than bankrupting money, then a Celestron RASA8 might be worth looking at,

Mount, mount, mount. The 'scope is the last thing to worry about. Does your SCT already have a good EQ mount? If not then budget for a mount first. HEQ5 level *minimum" unless you want to spent all your time fettling it. Then worry about what you're going to put on it. You talk about f/1.4 or 2.8. Have you budgeted for the ultra-high-speed NB filters to work at that ratio? At that speed you'll be looking at camera lenses, and not very long unless you're prepared to pay serious money, possibly into 5 figures. Fast 'fracs are seriously expensive as they get down to f/4. The Vixen VSD100 is f/3.8 from memory, and getting on for £6k. A Tak FSQ106 plus reducer will get into similar territory, for similar money. This is especially true if you want stars to look like points, and not seagulls. If you start thinking f/4.5- f/5 then you'll have a better chance of finding something affordable, that will give reasonable quality.

Yes, the teeth are for a follow-focus unit.

Yes, I should think so. If it's calibrated in T-stops then it will have been made for cine / video use. You might find it has a de-clicked aperture ring.

I went with one of These terrifyingly expensive roof automation set ups. Add a Cloudwatcher and if the weather deteriorates during a run it will park the 'scope and shut the roof. There are sensors to tell the system that your 'scope is parked, and when the roof is open or closed. The difference between the Talon and a bodged together garage door thingy is that this is designed and built for the job. Plus Rupert at Astrograph provides superlative after sales support.

571 sounds like the sensor designation rather than gain, but looking at the graphs on the FLO site going much above Gain 100 will lead to lower DR and Full Well. Going to Gain 400+ will cause catastrophic loss of both. Looking at the spreadsheet and scrolling right down to the bottom I see an awful lot of saturated pixels. For the next try I would keep the gain no more than 100 (Where the HGC kicks in. I might even go for Gain 0 to maximise Full Well. The Moon is a bright target! BTW "Exposure Latitude" is something I used to hear about with film photography (Been there, done that).

What gain setting did you use? The IMX 571 cameras should be good for 14+ bits of DR. How was the histogram? No saturated pixels?

Very much WIP. This is just the preliminary H-alpha stack. I took 40 x 900 sec Bin 1 subs with the ODK rig over two nights, but the last sub on each night showed some trailing as it had run off the corrected path. 38 subs were pulled into DSS and the best 90% stacked (Kappa-Sigma) with full calibration. The resulting 32 bit FITS was imported into AstroArt 7 and given a Histogram Stretch with curves, Gradient Removal, and a light Unsharp Mask. This is a slightly cropped JPEG to remove the alignment edges. Still some gradient, but this will do for the time being.

Yep, squeeze what you can in the car / van / lorry / pantechnicon / whatever. Even better, do as I did and *move* to a Bortle 3-4 location .