DaveS

Or maybe not. Looking at my ancient pair of Carl Zeiss 7x50 Jenoptem glasses I see that the interpupillary scale is reading about 68 - 70 mm, near the end of the scale. Maybe I just have a big head lol.

Having been trying them out I can report that if you have normal or wider interpupillary distance then you may find it impossible to get the two images to fuse. I have, what I consider to be, fairly average distance and the two eyepieces were hard on their maximum spacing. Suspect these may have been designed by / for/ people with small interpupillary spacing.

Thanks Bob, yes I'm coming to like the blue and gold rendition myself. that might be a good starting point for further work.

Looking again, I think I prefer the colour rendition of the left-hand version, but think the right hand is closer to a classic HST palette.

You could put a Filter Holder in the imaging train. Without a UV / IR cut filter you will get considerable star bloat from uncorrected colour in any refracting telescope, yes even the eye-watering apos.

From the FLO sale. A pair of Opticron Binos. I'd been looking for 10 X 50s for my old eyes.

Sure, but I had the [NII] filter in the wheel from an abortive attempt on M27, so thought it would be interesting to see what came up here. The [NII] signal is a lot stronger than the [SII] but now I have my [NII] data I will swap filters and go for some [SII]. I also had good results from the Rosette nebula in NHO.

Now for a comparison. Two versions, the first is the Blue and Gold that I posted above, the second is a Green and Gold version using a different set of Input and Output mappings in the RGB synthesis. Thoughts? Probably neither is "right" but what is the most likely reference / starting point for further work?

OK, @Adam J Three stacks given linear stretching only, left uncropped. I have tried to get each to about the same levels but as I was doing by eye cannot guarantee. First Hydrogen Next Nitrogen] Lastly Oxygen You cannot say "This is all Hydrogen" or "This is all Nitrogen" unlike with Oxygen, it's more a matter of proportion.

I've had another go. No DDP this time, just histogram stretch. Did a Linear and Vignetting gradient removal on the Hydrogen and Nitrogen stacks (The Oxygen gave banding), and an Adaptive Subtract on the RGB stack after cropping, then three (Or was it four lol) rounds of Histogram Stretch with one of them curves. Slight colour balance and another Linear Stretch, to give the moody, mysterious look I was after.

Melotte 15 is the cluster of very massive, very hot stars in the centre of The Heart nebula in Cassiopeia that's making the whole nebula fluoresce

Dur... yes, 10 min subs. Teach me to post in a hurry, lol @Laurin Dave, here's a rough stack I did earlier. The FITS on my computer is still unstretched. The [NII] does tend to reflect the HII, and even with 3nm filters there is still about 15% overlap. When I get another good clear night I'll try for some [SII] data for comparison.

Thanks James. It needs a lot more work, and I have some ideas as to how to proceed. I think I will try some first pass gradient reduction before RGB synthesis using just linear and vignetting, as the alignment edges mess up the fancy adaptive methods, and I need to keep the individual stacks uncropped before RGB. May try some channel blending as well, though that means the image is no longer a pure NB that can be decomposed for scientific analysis.

I'm not entirely happy with this, too messy and gaudy, but I'll post anyway as it will give a starting point for comparison later. This is "pure" NHO with no channel blending. 16 x 10 sec subs Hydrogen, 20 x 10 sec subs Nitrogen, 24 x 10 sec subs Oxygen through 3nm Astrodons. 130mm f/7 TS apo triplet, SX Trius 694 Encoder guided on ASA DDM60. Each set of subs was stackd Sigma Average, then RGB combination followed by cropping off the alignment edges and giving Adaptive Subtract gradient removal. DDP then a single round of linear Histogram Stretch. No noise reduction yet, but a slight colour correction to reduce the magenta cast in the shadow areas. Edit: Thanks to Laurin Dave, the subs are 10 Minute, NOT 10 Second. Dur....

The last time I saw that it was due to a telephone wire I hadn't spotted, but there could be a hair in your image train.

I'd be inclined to keep the 383+. Mono is faster for acquiring data, plus NB is FAR better with a mono camera, If needed you can add a LPF to the wheel for your Luminance, while keeping the RGB filters.

Even in your example above, M31 is bleeding off the corners, and I suspect that one of Olly's really deep images would be severely cropped.

The last small sensor square format cameras were based around the KAI4022, which had several attractions for me, but the low QE and high read noise put me off, plus they were un-cheap. The ASI533 looks very attractive, if a little small. No, I cannot afford one of the KAF16803 cameras, let alone a Kepler 4040 (Or even the 6060 ) Square format has a lot to commend it for getting the most from the image circle, plus you can ignore questions of orientation. I already have an ASI183 on my TS 80mm f/4.4 but am seriously thinking of swapping it for an ASI533. If only they did a mono version *sigh*. BTW, you can still buy 120 film.

80mm f/4.4 352mm

I've just run the figures through Astronomy Tools using my TS 80mm f/4.4 and it looks an interesting match. Slightly large pixel scale at 2.2"pp but not too bad for a short focus / wide FoV. Would get all of M31, M42 and Running Man, and Markarian's Chain with M87 plus a couple of others. Damn. see my sig .

Even the original Cooke Photovisual Triplet from the very early 20th Century used some rather exotic (For the time) glasses, to the point that the first iterations came a cropper due to one especially unstable element. I think the first one made was a 9" f/15.

Well, Astrograph are listing the TEC 140 at over £8k, so this looks a bargain by comparison. Mind you, the TEC does have a fluorite element.

Thanks Ade. I looked at their website and it looks active, the next meeting is Fri 13 Dec.

I did a search for nearby astronomy clubs and this came up http://www.weymouthastronomy.co.uk/ Anyone else heard or have experience of it? Looks to be about 25 mins or so drive from where I live, mostly along the (Unlit) coast road, so I was thinking of giving them a go.

Yes, this debate can run and run, but I won't hijack Haim's thread further by continuing it here. Just a pity that the Rho Ophiuchi star clouds are so low here and buried in clag, even from Dorset's Jurassic Coast.