Thalestris24
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Everything posted by Thalestris24
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Hi Gina Excellent - thanks! I'll give it a go if I ever get my mono 1100d back from repair... They've had it since the end of July, lol Louise
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Apologies for interjecting but how do you process raw files from a debayered camera? Any commercial software will assume the color matrix is still present and process pixels accordingly. Is there some software that allows you to tell it that it's now monochrome? Thanks Louise
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Looking for beta testers of new Polar Alignment utility.
Thalestris24 replied to themos's topic in Discussions - Software
Hiya Yeah - strictly... There's obviously reasons why trying to measure PA error can't be done too far from optimal positions. However, AT does seem to have a certain tolerance. As you know the East or West is just for alt adjustment. Fortunately I can see due East or West but I would imagine +/- 15deg would still be fine, maybe even further from due E/W would still be possible. Having said that, I'm not certain how near to the horizon you have to be to get an accurate alt error. The link below suggests measuring at about 20 deg of altitude (not too low because of atmospherics). People seem to recommend between 20 and 30 deg. There's some drift aligning theory here: http://www.shadycrypt.com/pages/Collins_derivation/Derivation.htm (From my flat) I can't see South for az adjustment. I can only see at either about 150 deg (East side) or about 240 deg (West side). Still seems to work ok for adjusting az (at least for imaging with shortish focal lengths ). As I understand it, if you can achieve negligible az error then you can still correct for alt error at some distance from the optimal E/W measurement position. I try and make sure my az error is at least minimised before measuring/adjusting alt anyway ( http://celestialwonders.com/articles/polaralignment/MeasuringAlignmentError.pdf ). I did come across a site that reckons you can PA on a single star - http://celestialwonders.com/articles/polaralignment/StarOffsetPositioning.pdf Louise -
Looking for beta testers of new Polar Alignment utility.
Thalestris24 replied to themos's topic in Discussions - Software
Hi Russell Astrotortilla combined with a little utility called polefocus (http://www.scopefocus.info/polar-alignment) does that! Louise -
I can see lots on the right (top and bottom)! Might some low-melting point gluesticks dribbled on be used to protect them? Just a random idea... Louise
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Hi It's ok, mine are fine and do their job! Thanks anyway Louise
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Hi My lever sits parallel to the housing when tightened. If yours doesn't then I expect the lever position needs adjusting. HTH Louise
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I wouldn't buy 2nd hand but I might try the ST-80, just to get experience of taking everything outside, transporting it and setting up etc.
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Hiya It might be a reasonable price but I can't afford it! Louise
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Hiya Ok. Yeah a budget essentials version maybe a tested reject or something... But still, might be worth going for. Nice to live near a showroom. You must have quite a collection of scopes now! The Ascension 80 looks nice on the Opticstar page, if a bit too expensive for me... Thanks Louise
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Hiya Oh dear, I'm 'cross-threading' myself here... Started a separate one asking about the TS APO 90mm... As mentioned at various places, I need something I can attach a filter wheel and dslr to... This is a headache with most flatteners/reducers. The TA APO 90 / Revelation has the advantage of being useable for imaging without a reducer though still needs a flattener of course. The Zenithstar 71 is also fast enough for doing that but is a little short. Still, I'll put it on the list! Do you still have the Ascension 80? I saw a couple of images you did with it - looked fine to me! Thanks Louise
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Hiya I'm not sure how transportable it would be and I know fast newts are critical to collimate. Plus I'd probably run into the backfocus problem with any newt. A short frac fits the bill better even though the cost is much higher. It's frustrating that I could buy a 130pds for less than the cost of a field flattener but that's the way the scope cookie crumbles! Thanks Louise
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Hi It's a little short and only has 35mm focuser travel and seems a bit 'non-standard'? It's a bit pricey... The Equinox is a bit pricey as well really, especially, as you say, with the flattener (+£170). Sigh. I've been pointed in the direction of the Explore Scientific triplet ED 80 Essential which is less than £500 incl shipping and has good reviews. There must be a crossover where there's a point that it doesn't make economical sense to pay more for a scope that's to be used with a dslr... The intention is to image with narrowband as I already have the filters but osc and LRGB are still an additional option. I might find that I have less lp looking to the west, away from the city, in which case non-narrowband would be much better than I get from my living room! It's like a lot of things - don't know until I try! I might simply postpone getting another scope and simply try out with my ST-80. It's pretty rubbish for imaging but will give me an idea what al fresco imaging would be like and the kind of images I could get looking West. More deep thought. Anyway, I still have to get a laptop and some other bits first... It all adds up! Thanks Louise
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Hiya Yeah, I'm aware the two scopes are the same in that respect but I don't want to disturb the 150pds setup. It sits there quite happily, all focused and ready to go - should there be a break in the clouds! Besides, what would be the point of doing it? I already have a modded 1100d I could use and using a colour camera for narrowband is inefficient anyway. I'm looking at other refractors like the Equinox 80. It's a bit pricey but cheap compared to true APOs and easily portable. I can get a flattener with a long back focus which would give me plenty of room for a filter wheel. Thanks for your input though - much appreciated Louise
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Hiya Um, it's not really about pressing stuff into service, it's more the need to have a portable combo I can easily take outside (I live in a 2nd floor flat with no lift...) and that's quick and easy to setup - and on a tight budget, of course! The 150pds would just be too difficult for little me to transport. A shortish refractor seems to fit the bill.. It would be a shame to not use the mono 1100d. In any case, with the local lp, narrowband seems the way to go. A filter drawyer might do - how much focus travel actually is there with the Evostar ED80? Maybe an alternate ED80 make/model would allow it? There must be a way!! I know a mono ccd would be the best solution but I just can't afford one Louise
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Thinking about it, I suppose the focuser travel is lost by using a focal reducer... I only need 25-30mm for the filter wheel. Maybe an alternate refractor? An achromat might do. I suppose I could swap speed for space. Oh well, back to deep thought... Louise
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Hiya Luis seems to just use a single filter (Ha) and blends with colour images from an undebayered camera. He has some very nice images on his Flickr page. I was thinking about having the fw ahead of the Evostar 80ED ff - there must be plenty of travel room since, without the diagonal, you'd have an extension tube attached? However I don't know if there'd be a problem from an optical point of view with filters further from the sensor? Thanks Louise
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Hiya Oh, I should have said... Yes, with a debayered 1100d. Hmm... I'd forgotten about the 80ED slowness. Can't win, sigh. Do you think it might be feasible to attach a filter wheel in front of the ff? My qhy8l is permanently attached to my 150pds which is staying indoors. I'm trying to put together a rig to use outside and which I'd be transporting to a location which is about 10mins walk away. Louise
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Hiya Thanks though I really wanted to know if one is better than the other in terms of use without a cc/ff since I want to be able to use a filter wheel with a dslr... Maybe there's no difference? Cheers Louise
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Hiya Yeah but can't have cc+fw+dslr as far as I've been able to ascertain I don't suppose anyone has had experience of 130pds and 80ED - would be good to have a comparison re: distortions. Louise Louise
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Hi I'm still thinking about getting one of these... I guess it needs a coma corrector? I'd really like to be able to use a filter wheel and a dslr. I'm wondering if the coma on the 130pds is worse (or better) than the field curvature on the Evostar 80ED - anyone know? Cheers Louise
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Hi again Can you confirm if you have reducing coma corrector? If it's a SW 0.9 one then your fov will then be 1.41 x 0.94. So 20% bigger will be 1.41 x 1.2 -> 1.69, say 1.7 and 20% smaller will be 0.94 x .8 -> 0.75. So those numbers will determine the index files you need and you can put 1.7 into scale maximum. Hope that works now! Phew! Louise
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Hi again Actually, your fov calculation is wrong - for a explorer 200 and a 1000d, it should be 1.27 x 0.85, so 20% larger should be 1.27 x 1.2 -> 1.83 deg, say 1.9 deg. 20% smaller should be 0.85 x .8 -> 0.68 deg so you need to use those values to determine which index files you need. Then you just need to put 1.9 into scale maximum. I suddenly realised your calcs were wrong when I was looking at my own for a 150pds and 1100d... Sorry, wasn't thinking before, d'uh. Louise Oops! Sorry just realised you have a coma corrector - if that's a reducer also, you'll have to multiply the values to allow for that.
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Hi Assuming your fov calculations are correct, the scale maximum value should be 0.282 degrees - say 0.3 in round numbers I don't think you really need to specify the scale min value (can be 0) or the -H and -L parameters. Hth Louise
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Wow! Need my sunglasses on to view that one!
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