Thalestris24

I think the shift can be quite noticeable (without a diffuser). Clearly, if both electrodes in the bulb are glowing then it could appear as two sources with light hitting the slit at different angles. I'll try and sort out some sort of diffuser for mine Louise

I've noticed that too and realised I need to make a holder for it that fixes its position (something I still have to do). It's probably an effect linked to the variable spread of the source close to the slit. I've actually been using a Sylvania 70W starter bulb which is bigger than the Relco. The Alpy calibration unit has the bulb fixed in place and I think uses a DC power supply which will only cause one side of the bulb to glow. I had thought that wasn't such a good idea but now I'm not so sure.... Louise ps it's a good idea to use a reflector - I just have some Aluminium foil wrapped around mine. There may be a better way...

The sensor back focus won't be the same. If you have a reducer you'll probably have to insert an extension tube. Always a good idea to get close to infinity focus during the day with a new camera. Louise

Alas, thick cloud, wind and rain here as Storm Ciara rolls in... Batten down the hatches! Louise

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It occurred to me than a small EL panel might do for taking flats with, so I ordered a white 5cm x 3cm off Ebay. I'm not sure what the spectrum will be like but, since it's a white panel, it should be broad. It might be possible to fit one inside the Lowspec case else maybe in a filter drawer/changer which are ~5x5cm. I ought to be able to simply switch between the output from an EL driver to either the starter bulb or the EL panel. I've no experience of using EL devices so it should be interesting to investigate, if nothing else . I don't know quite how bright they are. If they are quite bright then maybe could simply fit one to the floor of the case? Will have to experiment... Louise

I just ordered a couple of the EL drivers. They are ridiculously cheap - 2 for £2.30 plus free postage from Singapore, lol. I wonder if the Alpy design with the mirror is protected? If not, I guess it would be fairly easy to do something similar with a mirror. I'm not sure why they've used a halogen bulb for the flat field source, I'd have thought a white led would do, though I'm not sure of the spectrum you'd get. Louise

It may use a DC-DC converter circuit similar to what Dr Jolo has posted. The DC-DC boost circuits use a small inductor rather than an actual transformer. The EL driver I linked to has a 120V AC output - it's also very small (4 x 1.8 x 2.3cm). As it's only 120V it's safer (though could still give a noticeable jolt!) and may be ok to run a starter bulb without a resistor. Louise

Yeah, one of those would work to generate the voltage. The only trouble is that it's a dc-dc converter which means that only 1 half of the starter bulb will light which is why I've steered clear of them. That may not be a problem in practice, I'm not certain, but it may affect the life of the bulb and may affect it's behaviour. Certainly worth a try! Louise

Actually had some clear sky tonight so had another go with the spectrometer but didn't achieve much. I'm not sure my equipment or location are really suitable for doing slit spectrometry . I basically had the same problems as last time, made even more frustrating by usb problems and things disconnecting - grrr! Running 3 usb cameras concurrently is quite demanding. As before, I had trouble getting stars in the guide cam fov. I had to mess about pretty much trying to guess where a star actually was by using the Celestron driver arrows to move the scope this way and that. Then, if I got a bright star in the fov and then on the slit it was too bright to guide on and there weren't any others around to guide with. PHD2 seems to blank out dimmer stars when there's a bright one in the fov. Is there a way to circumvent that? Doesn't seem likely. I tried to acquire a spectrum of a bright star (Alphecca) unguided but nothing came out on the Atik383l+ even with binning 4x4 and a 90s exposure . I say nothing, but stretching the image did reveal a faint horizontal line and a short vertical one too. The Atik isn't very sensitive… I was a bit concerned when testing with a starter bulb as even that took 90s to get a decent image. What would anyone else's typical exposure time be for a single frame on a brightish star? I think my only way out of these problems would be to get new cameras but that would be rather expensive. Louise

Hi Paul I guess that Richard Walker inverter (see doc below) is about the simplest though you'd have to build it. As far as I know there aren't really any commercial very low power inverters around. At least, I've not come across any and there's not going to be any demand for them. Having said that, one of these electroluminescent wire drivers might work. They take in 12V DC and output 120V AC so should do the job. I suppose they actually do come under the definition of 'low power inverter'.... Anyway, they are quite cheap Maybe try one out? inverter-12v-dc-_-230v-ac-3.0-englisch.pdf Louise

* e-finder

I'm wondering whether to splash out on an alternative guide cam - maybe the qhy5ii, though it's not as sensitive as the qhy5l-ii, but it would give a bigger fov of the slit plate. Also, next time I'll try and remember to bin the efinder 178. Louise

Yeah, I probably should have done PA via the travel scope. I probably wouldn't have any trouble using the Travel scope to guide with (it was being used as a guide scope before, but with a gpcam mono) but the 178 camera doesn't seem sensitive enough but I'll try it with PHD next time. As I said, I could get a bright star on the slit plate but it was too bright to guide on. I'll give it another go next time. Thanks Louise

Hi Ken I had a quick go tonight but, as I expected, it wasn't easy and I wasn't very successful... I did initially centre on M44 (Beehive cluster - lots of quite bright stars) and was able to nudge a star on to the slit. It wasn't too difficult to identify the star from the pattern of stars in M44. I'd have been lost if there was no obvious pattern. Anyway, at that point, I hadn't done any PA so a PHD calibration and drift align in DEC was the first thing I needed to do. But it was a bit of a nightmare as the fov via the qhy5l-ii on the slit is so small. I had to keep plate solving after adjusting because the star kept moving away when adjusting Alt. Hopefully, next time it will just need a check. Still, I eventually got the PA done ok. But there weren't many groups of stars in the East I could use for testing and I didn't manage to guide on anything. I'll have to have a look to see if I can tweak SharpCap/Astrotortilla to get the target star closer to the centre. I had trouble picking up not so bright stars in PHD whereas bright stars were too bright for guiding on, at least. Stars kept going in and out of focus and moved around a lot. I'm not sure that guiding at 800mm is going to work for me but I'll try again when I can. There was also quite a bright reflection on the Ovio such that it looked liked there were two stars. The transparency dropped and I couldn't get any more plate solves so had to pack up. There is nearly always a lot of moisture in the atmosphere here. Louise

Hi Ken I'm good - just waiting for some clear skies so I can do some testing. Louise

Hi What mount do you have? Are you intending to do imaging? If so, you'll also need an autoguider. Certainly you need to balance properly, polar align (assuming you have an eq mount) and then star align. Louise ps sorry, see you have an heq5. You might consider a Rowen belt mod to improve the mount's performance

See my post above, Ken. It's not the e-finder fov that is itself the problem, it's really my guide scope fov that's difficult. Maybe I should look at changing it but anything with bigger pixels and the same qe will be expensive, I think. Cheers Louise

Yep, yours is bigger than mine, Ken! Ha ha That's the window I image through... It's not very big... Louise

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Oh, the finder has a much bigger fov at full resolution (1.06 deg x 0.7 deg) but I did the final comparison/alignment at a similar roi to what's seen by the guide cam since both then show a very similar fov. Also, you have to remember my scope is in the living room which means I can't go anywhere near it when I'm normally guiding/imaging. If I just stand up it messes up the guiding! Louise

Well, it also has to be identifiable, so ideally needs to be seen (by me) as part of a pattern. The images I took of the Coma Berenices cluster above are quite thin on the ground in terms of stars with a small fov. I calculated the e-finder fov to be 26.4 x 21.2' and the guide cam was 20.5' x 15.37. Quite a small area of sky (for someone used to imaging dso's). I guess the side-by-side pylon pics show the reducing effect of the Lowspec guide lens. Louise

Hi Ken It may not be difficult if the target star is visible in the guide camera. If it isn't, it will be impossible!. It took quite a lot of effort to get the e-finder and imaging scope aligned well enough to get the Coma Berenices stars in the two fields of view. If I happen to lose that alignment after dark then that will be end of session... Louise

Mine is only F7... Louise

Hi Ken I was looking at it from the point of view of being able to plate solve a view and so get the star on or near the slit. The side-by-side pylon pics show the actual comparison. It won't be that easy in practice unless my e-finder is accurately lined up with the Lowspec guide image - even quite a small deviation will make it difficult, if not impossible, to find the target star. It also won't be that easy to maintain the alignment. Louise