DaveS

If I was content with a transmission type I could knock up another Hartridge prism, though the ones I'd made before were only for school level use, a 600 l/mm grating on the hypotenuse of a 90 degree acrylic (Yeah, rough) prism gave DV near the centre of the visible spectrum. I think the PH DV spectroscopes use a similar arrangement. Thinking, Jeulin do a 600 l/mm grating blazed in the 1st order for not too much money, cementing that on a right angle prism might be an idea. Mind you, I have a small Amici prism in my "box of bits" though the non-linear spectrum makes it no-go for imaging. OK for purely visual perhaps.

That's still a lot less than the £95+VAT for an air slit from EO.

Thanks, the OVIO slit plate looks a lot less frightening that the EO offerings.

Thanks for the replies and apologies for not responding earlier, I'm still giving this thought. Question: Where to get a reflective slit? I've seen a rotating multi-slit plate in @Thalestris24's build thread, Thorlabs? ATM I've been looking on the Edmund Optics site, they have air slits, but I didn't see the type I would want. As an aside, the slits I've made before were cut from brass and beveled tonear knife-edge.

Something to consider is that the HII line at 656 nm is nearly always the strongest in emission nebulae (PNs may differ), while the [OIII] and [SII] lines are often weak, or almost non-existent. You won't see the [SII] and [OIII] lines in the solar spectrum as they are "forbidden" and only seen in very rarefied gasses. [NII] ,ight occasionally be strong enough to be moon-proof. 3 nm filters have the edge here.

No, they're NOT geostationary, they are in LEO, which means even more streaks across your subs.

AstroArt has a line removal tool and if you take enough short subs (Though subs have to be long enough to overcome read noise) and use sigma stacking that *might* get rid of them but it's still a hell of a lot to remove.

I'll put it on the target list for the ODK12 when I get it up and running, though 2040 mm might not be enough.

Lovely image. I've got this on my hit-list (Just re-started it) but will have to raise my game enormously to come anywhere close. Love that braided dusty loop just emerging from the orange clouds on the left.

Prefer the delicate colours in the NB image, which also shows more of the structure.

I don't think Musk thought of anything beyond "Because I can" . It's the only reason egomaniacs like him need.

Mr DPD delivered another big box from Scan I think it helps if you can see your images as they really are. Impulse purchase really, Scan had this on offer (Supposedly) reduced from £700 to £430.

And I'm fairly rural but have 4G mobile and 65 Mbps broadband. Some of us, eg Gina, have gigabit FTTP.

No, they're not geostationary, he's putting them into low earth orbit.

Signed and shared. Won't make any difference though, money talks . Money, money, lots of money, grab grab grab.

Ooh 🍿 . I'm trying not to think about how much I've spent on imaging kit, but it's a fair bit more than my car (Which wasn't cheap either)

Imagine guiding the 200" during several hours exposure. I think us imagers today have it easy . I remember reading an account of the building of the 200", where they made the driving wheel in two halves, so they lapped it, split the halves and rotated them through 180 deg and lapped it again. They then repeated this with 180 deg - 1 tooth, rotate 180 deg -2 teeth etc to get the most error free drive they could,

Many thanks guys. I think I will apply the KISS principle to my design and avoid off-axis paraboloids, though it seemed a good idea to avoid a change in focus with wavelength. Much to ponder in the linked articles. It's likely that I will use a "basic" ruled grating of 600 lines. Whether I will source the lens from Edmund or use a S/H photo lens remains to be seen. Off to do some more research, but in the meantime I may well buy a SA to go in the filter wheel of one of my 'scopes.

I've ordered a couple of 1m cloverleaf IEC leads, should come tomorrow.

There is an external "brick" PSU that has an "odd" 3 pin connection with the pins in separate receptacles, while the mains lead has individually insulated sockets. I've seen this before on other (UK plugged) power supplies. If I knew / was sure of the colour coding of the wires in the lead I'd cut the old plug off and wire a UK one on.

It would have been even nicer if Thecus had supplied a UK plug (Is this even legal?) . Fortunately I remembered I had a couple of adaptors from a US / Chinese battery powered monitor for their chargers so was able to use one of them for this. Still not happy though.

Well, as it would go on (Most likely) the ODK12 at f/6.8 (Call it 7 for now), and to maintain throughput the f-ratio of the collimator should equal that of the telescope, then if I use a 25mm dia mirror then I get a fl of around 175 mm. I'm not after super high resolution, but as a ballpark figure I would want to split the Na D lines, so 2000 or so. I hope to be able to put the visible-ish spectrum (Say 380-780 nm) on the whole of a sensor, which could be an ASI1600 or perhaps an ASI183. Maybe. Perhaps. I'm open to the possibility of having to move the grating to select narrower regions of the spectrum. Note the vague design specs, this is because it is at a *very* early stage, of still kicking ideas around, I haven't even done any precise calculations yet.

Just kicking ideas around ATM, and don't even know if I will proceed, but do any of the experts on here have any experience / thoughts on Littrow configurations? ATM I'm thinking of an off-axis paraboloid for collimation and focusing, and a small flat mirror at 45 deg to divert the beam into the camera. Also considering a 45 deg pellicle beam splitter to divert a portion ( ~32%) of the input light to a guide camera. Ideas are fuzzy as yet, and not even down on paper. I've cobbled together a few spectroscopes in my time, but nothing as critical as this.

Mr DPD delivered this The company name might be a clue for those who know. Inside was And four of these A NAS box and 24 TB of storage which I'll set up in RAID 5 to give me 18 TB net. I did consider RAID 6 but would need more drives to not eat into the storage too much.

That's a cracking image Ian, huge amount of data, and an absolutely tiney PN. Just seen how many nights of imaging this has taken, a real marathon effort. Interesting to see someone else using [NII] in their imaging. Have you tried it with other PNs, or even other emission nebulae? I found quite a lot in the Rosette Nebula.