Well, did some experimenting and then just plopped the whole plossl/Micro stack in to actually get some viewing in without experiments. F/1.4 for viewing through the 150ST tonight.
My camera experiment:
Straight through with field flattener and focal reducer - would not come to focus. Ran out of back focus.
Imaging train was D3300 - Litton Relay - Litton M942 - c-mount to T2 Adapter - Orion FF - Antares .5x reducer - 640nm Longpass. Probably 15mm shy of focusing. Could see out of focus stars.
Straight through with two .5x reducers - would not come to focus. Ran out of back focus
Imaging train was D3300 - Litton Relay - Litton M942 - Scopestuff 2” c-mount nosepiece - 35mm extension - Antares 2” .5x reducer - 35mm extension - GSO 2” .5x reducer - 640nm Longpass. Should have tried reducer direct on nosepiece and one 35mm extension between the two reducers or a smaller 15mm or 20mm extension between them.
Straight through with two 35mm extensions and .5x reducer - this worked and came to focus
Imaging train was D3300 - Litton Relay - Litton M942 - Scopestuff 2” c-mount nosepiece - 35mm extension - 20mm extension - 15mm extension - Antares 2” .5x reducer - 640nm Longpass.
With final configuration using 70mm of extensions and the Antares 2” .5x reducer, I swapped out filters for my 3nm Ha filter. After focusing with stars at ISO 800, I cranked up the ISO to 1600 to get live nebulae views. My 2nd lcd tilted 90° from the camera worked good for viewing but ISO 1600 is noisy. All my single shots were a noisy mess with that Omni IV tube, aggressive filter, and high ISO.
The unexpected bonus - I was not in bulb mode and I think my infrared shutter remote battery is dead or I was at the wrong angle or it needs bulb mode. I can’t remember but think it works when not in bulb mode. I’m unfamiliar with my camera and doing this again because it’s been so long. I accidentally took 2 short 60 frame per second 1080p movies and did not discover this until after I put almost everything away and replaced the battery in my camera. I was checking the stills and saw two short movies. I should have taken longer ones. As soon as I started the playback, the noise went down considerably and I got two mini movies showing a very bright Lagoon with a good deal of scintillation still but tolerable for how bright the nebulae was. I need to experiment more with this. Still possible I can reduce further with the right combo. I was around F/2.25 from the looks of the FOV. If I can get it to F/1.2, the live movie mode will actually come out pretty decent with my manual mount. In one of the movies I switched ISO while filming and even at ISO 400 I could see some nebulosity in real-time. At 1600 it was very bright but a bit noisy but nothing like the noise of the stills. I think some further experimenting might get me some real-time movies of nebulae viewing and very bright. If I can reduce to F/1.2 - F/1.4 I can bring down ISO to 400 and still show very bright nebulosity without as much scintillation. I was almost there with what I thought to be an acceptable live nebulae view video. I hesitate to use a less aggressive filter, but would rather concentrate on getting f ratio down more.
Next time it’s clear maybe and clear all night. Forecast said clouds around 12:30 and was correct. Clouds started rolling in. If I can get a full night of no clouds I can figure out best setup for some nebulae video.
I did not try my pvs-7 with field flattener and reducer. I don’t think it will work anyway. Ran out of time. First hour and 20 minutes running my experiments, then swapped out to afocal F/1.4 setup and relaxed while viewing some great nebulae.
The more I think about this, the more I’m convinced I can get the focal reduction down below F/2 and lower the ISO. At ISO 1600 it also picks up IC1274, IC1275, IC4685 next to the Lagoon pretty well defined. I want that much detail but a little smoother in the video.
Edited by Vondragonnoggin, 10 July 2019 - 04:18 AM.