Gina

With widefield imaging rigs it's not so clear-cut. My earlier thought was to make a double bracket to take two cameras side by side but now I have the dual mounting bar there's a simpler option. Copy the current WF imaging rig and put one on each mount. One can use the 8 position ZWO filter wheel and the other the ZWO EFWmini with 5 positions. There then remains the question of guiding. Seems an OAG is not practical with lenses. Reason is that the back-focus of these vintage film SLR lenses is 45mm whereas that of the FF is 55mm. This means the distance from OAG prism to sensor is only 30mm rather than 40mm and the guide camera can't be got close enough to focus.

Now I want to sort out how to arrange dual imaging rigs and guiding. With telescopes it's clear - one on each mount of the dual mounting bar. Though I have just the one Esprit 80ED, the humble ST80 is same focal length and an achromatic scope is alright for NB with the very narrow wavebands, so an ST80 is adequate second imager. I also have a pair of Evostar ED80s both with focal reducer/flattener. The FL becomes 510mm and f6.37. In either case one scope can have an OAG for guiding.

There's also Light Vortex Astronomy tutorials. +1 for second edition of the book!!

Focussing doesn't need much power if you use the 10:1 reduction drive on a telescope focuser. The gearbox on the 28BYJ-48 holds focus even with a heavy camera hanging off the focuser. Note that my mod converts a 5v stepper into a 12v one though you could use the 12v version unmodified with the driver often supplied with it (the sketch is a bit more complicated though).

With the camera turned 70° rather than 90° the framing for the Heart Nebula is much better.

Returning to the Heart and Soul, while these didn't fare well as a pair with the dual lenses, they do work as separate objects in the 200mm lens and Esprit 400mm scope. The Esprit can be "twinned" with an ST80 for a dual imaging rig.

M42 will fit nicely in the FoV of the Esprit.

Flame and Horse's Head in Orion with 200mm f4 lens and 400mm f5 Esprit 80ED scope.

I use 28BYJ-48 gearbox stepper motors for all my focusers (lenses and telescopes) modified to run off A4988 driver modules as per my blog

NGC 7822 is one nebula that will fit nicely in the 200mm lens field. As does IC 1396.

Heart and Soul. These don't fare so well - rather small for the 105mm lens but the 200mm looses some of the surrounding nebulosity.

Now to look at the DSOs I've been imaging recently. Flaming Star and Tadpoles. Simeis 147 - Spaghetti Nebula.

Been going through my astro bits and pieces to see what I can do to collect more data and more difficult data. Two main ideas - dual imaging rig and guiding. I only have one 135mm f2.5 lens (which I'm using currently). I also have just one 28mm lens. OTOH I do have three 105mm f2.8 lenses and three 200mm f4. Then it's a question of matching DSOs with appropriate lenses or telescopes (starting at 400mm f5). The 105mm lenses give just under 30% more coverage in each direction than the 135mm. This is a fairly small increase and I think would probably be alright for the DSOs I've been capturing with the 135mm lens. I only have two ASI 1600MM-Cool cameras so I'm limited to a dual rig whereas a triple rig would be ideal, with Ha, OIII and SII NB filters. In fact the 1600s are the only cooled cameras I have. NO!! I can't afford another!! One DSO which is just too big for the 135mm lens but fits in the FoV of the 105mm is the AngelFish in Orion.

When I went over to the ASI 1600MM-Cool cameras after smaller sensor Atik CCD cameras, I already had 3nm Astrodon NB filters in 1.25" size. I am also imaging in widefield with high quality vintage SLR lenses used at full aperture. I have successfully been imaging with lenses of f2.5 in focal lengths from 28mm to 135mm. I use the ZWO filter wheels to get the filters as close to the camera as possible and do get a bit of vignetting but this is completely corrected with flats. 31mm unmounted filters should be a bit better but I haven't had the chance to test this. "Bottom line" :- with flats, the slight vignetting seems not to be any problem.

I have enough trouble with 32MB raw files and 64MB XISF format in PixInsight. Have to wait for entanglement computers to become available as well as win euromillions!!! Well out of my league as an OAP!!! As for filter wheel - build you own. 3nm NB filters... !!! Oh dear... my mind has boggled! 🤣

If I design and print a bracket for the focus motor that clamps onto the barrel of the focuser, I can have camera rotation by simply loosening the clamping ring that connects the focuser to the scope body.

Some new data for this from Tuesday, 28th January. Gain of 180 and exposures of 120s. In spite of an imaging run of around 4 hours I only got a total of just 30 subs that were at all reasonable - just an hour's worth. The problem was passing thin clouds. This is a screenshot of the result of calibrating, aligning and stacking in PixInsight with STF auto-stretch. Here's a series of different crops and stretches performed in PixInsight of the Orion image.

The FLO page for the ZWO OAG shows an ASI 120MC-S as guide camera!! Not the mono version. Well well!!!

I think that would be very helpful - thank you.

Interesting thread and helpful to me in giving a talk on astro-imaging. I expect my audience to be adult though there's no reason why children sholdn't attend. When I discussed my talk with the organisers of our group (Local village social society) they advised keeping it to no more than 45 minutes. I am thinking of taking a small telescope and tripod mount as I too think some hardware to show what's available would be good.

Widefield rig with 135mm f2.5 lens.

In fact I'm wondering about the Esprit 80ED and WF rig. The Esprit has OAG and maybe could provide guiding for the WF rig. A strange arrangement I must admit.

Now I have a heavy-duty dual mounting bar for my EQ8 mount I'm thinking I should be able to have an imaging rig one side and guide rig on the other - particular for widefield. I presume these dual mounting bars are intended for dual telescopes and a dual imaging rig. The kit is certainly very heavy and rigid.

I'm right back into astro imaging so spending money is par for the course!! 🤣

Just realised my ASI 120 is the colour version and I guess I should have the mono version or the ASI 120MM Mini which I could use with my Baader Click-Lock micro-focuser. Comments please.