SilverAstro

No worries Nige, I only mentioned the little box as an aid in identifying (with Ian's help) which picture I was not seeing, all sorted now = a fault with my browser which will have to be replaced !

Thanks Ian, the plot thickens, it is Nige's 1st one PSX_20160709_031747.jpg.8ba22b25002c6d8aaf4f284fb7c5ffd6.jpg that has gone AWOL, I can see it if I revert to Firefox but for some reason yet to be determined K-Meleon ( based on Firefox) cannot see it and even worse did not put up a blank icon to signify I wonder what else it has been not showing me I think a trip to K-Meleon site is on the cards !

yep really now I am seriously worried, what is going on, the top one is pale, the middle one is orange-ish with a "Paint" dialog wee box lower left and the bottom one is pale yellow with ummm yellow-green in the spiral, but the sun is creeping up on my monitor , how strange These are the 3 part URLs PSX_20160718_215237.jpg.c1dce7c6219f4a10aea5dda143a7306e.jpg PSX_20160718_215704.jpg.10c2840ba70cc6f89d9f1f9aa2615d6c.jpg PSX_20160719_121341.jpg.d8d0b5fd53451753223adbe6c4ccbfeb.jpg which am I missing, is it also a jpg or something else that my browser is rejecting ? What if I re-quote it all , how many remain ? :--

Oh ! I am amazed, I thort you had a modded one, , , and isnt the NA mostly Ha emission ? so you are not lacking for much, mummble mummbl, think I'll forget all this stuff about measuring the response of various and just go buyme a 1200d like wot my chum Nige has Luvverly stuff, but am I going blind - I can only see 3

But I like it so far, good laterals !

Perfect example of the sort of embryo that was in my mind, thanks SM, 2 cameras from the same source brill ! Do you still have the frames as they came out of the cameras so you can do the same (or lack of !) processing on them both ? Just by way of example of how I thought a protocol might develop here is what I was thinking we might do in IRIS, it has a slice tool to take a histogram across an image, first I reduced them to b&w to compare levels, we could discuss how to compare colour amplitudes in a colour image later(?) Iris did not allow me to do a screen capture of where I placed the slice so I added the green arrow later in the approx position , the slice on the left shows that the level in the Ha light region ( short green line ) is well below that in the right pic (and as I type this Ian has added a right good idea !) but let me not waste my cunning Iris plan :-

Good candidate (I think, but my knowledge of it is limited !!) and that is the big problem, how to avoid processing distorting the ratio, it may look pretty but may not be quantifiable. Some way of doing it raw-ish would need to be defined Very interesting folks, cant stop - due into the clutches of the NHS, will be back later to comment better

Yes, Orion in the offing that is indeed why I am contemplating a new camera, be prepared, boyscouts etc initially for wide field. Thanks for your suggestions. My initial thoughts are for a nebula in which the two regions are reasonably distinct ( not overlaid or jumbled up ! ) such that the reflection could be used as a broad spectrum reference level and the Ha signal amplitude compared to it. So aperture should affect them both equally ?(I think ?) Light pollution hmmm yes good thinking that could be a bit of a nuisance (!) to quantify, especially if the pollution had strong emission near Ha (??) and it would rule out pollution filters I suppose - that could be a bit of a killer of the whole idea A limit on subs, yes another problem area, if the sensor was differentially non-linear ? are they, I am rapidly getting outa my depth here !

In the end I suppose I could buy one of each and try them ! Oh, hang on an idea is germinating, , , , "try them" measure them !! Nige, Admiral, me and others I am sure like a good experiment soooo being as there are many owners of many models, mod and not mod, on the forum can the collective come up with a standard model (standard target?) and standard method free of user bias to determine the %Ha for each ? Henceforth to be known as the loadsaHa challenge " %Ha Challenge" Edit PS is it a bit odd that Canon have different filters for different models ? For viz light cameras one would have thought that they would have determined an optimum cut-off and stuck to it through the range ?? EDIT 2 ) A. a reflection and emission nebula in close proximity, ie. a convenient field frame size B. stacking OK ? but no curves / gamma etc. C. ?

A very nice example, yes I see ! As I am trying to decide between a 1200d{mod or maybe not} , a 1300d{not}, or a 100d{not} but not got a clue about their %Ha ! (and I dont think Curry's will be able to help ! ) where would be a good place to get this info ? Apart from Nige's excellent work ,, another pic some time ago, I forget where, was of Barnard's Loop next Orion, and in mod/not mod comparison the loop was not visible at all without the mod, now I am kicking myself cos I did not note the make of that camera

Very good ! +1 for the first one, unreduced.

interesting that you should raise that - my first polar disc mount used a strut + wheel hub off a Ford Zodiac, amongst other bits and pieces ! But cars are not usually steered with arc second accuracy

Yes, exactly my worry hence my "Can regular eq mounts be sold to people living close to the north pole ?" I know there are general solutions to handle it, eg. in the case of star sensors on spacecraft, but I cant remember how (that wasnt my prime responsibility ) nor if it is implemented in these softwares. We need an experimenter Side line : another thing, I've never been happy with German equatorials, too wobbly perched on top of tripods with their bearings way too close together on the shafts for stability, but if one of those shafts is turned vertical(ish) then maybe not so bad ?

Mechanically that is certainly true, bent bolts and all ! But if the software is capable of handling the spherical coordinate shift to working vertically at the pole then there is no reason (?) for it not to work in London if it were de-wedged and told a little white lie ! (In other words it would need to pretend to be working at the centre of the earth, ie. only good for geocentric not topocentric coords. ( good for stars,dso etc, not nearby solar system ) I think !!

EDIT Can regular eq mounts be sold to people living close to the north pole ? In which case one could be used in London with an appropriate tilt, the software would not know that you were lying when you said you were in Svalbaard or wherever ! Caveat, that will only work for geocentric coords, so the moon and close asteroids would not be tracked correctly (maybe not even the planets ? )

The Celestron SE mounts use spur gears, the Evolution mounts use (supposedly better) worm&wheel and was big in the publicity when they were introduced, I dont know what the Discovery uses ?? I suppose a big beefy eq could be de-wedged ! depends on how clever the software spherical trig is I suppose. Does the jerkyness of the mount tracking mean that it is advantageous to use many short exposures, even in the East or West where 90sec could be done it may still be better to do 9 x 10sec say, and give DSS a better chance of using them ? Blue star bloat in (who's was it ?) Achro, wild idea = is there such a thing as a red & green pass filter ? a 2 position filter wheel with exposures made by red&green + blue. Thus similar as the big long boys do R + G + B + luminance + whatever other channels they fancy ok I'll get my coat Nige - fingers and everyting xxed for your Mum, best wishes.

Hmmm I'm not sure I'd go along with myself either ! and I agree with Calli ( I am being very agreeable today, , even though I have just returned from the clutches of the NHS myself ) that it is a bit ott for amateur alt-az, but from PMs with Nige I know he likes a mechanical challenge So, deffo in the experimental challenge category ! Thanks for the link to the software control, I expect Gina could do something with an arduino as well ! Just for curiosity (?!) an alternative to the complex maths to follow the 'nodding' field rotation motion, that I read about somewhere ( sorry lost link) , is to use an off-axis guide to follow a rotating edge of field star. Ok, back to reality sorry for the diversion > > >

echo Ian, and best wishes from me.

On second thoughts, a field derotator would probably disqualify for "No Eq" as it is just another means of compensating for the earth's polar motion, an eq mount by another name/philosophy !

The minute you said that I felt sure Nige would second the motion when we put this to the committee Ah yes I see, note that I have cut out "big", on the grounds that your results are already amazingly impressive ! So, mindful of your desires and knowing of your mechanical skills and expertise with a lathe, how about a Field Derotator ?

I fear I might have lost the plot here ( long day + some amber nectar!) - but why do you want to downscale from your 150 reflector to a 130 reflector ? ( going to a refractor is a whole other kettle of fishes ! ) In an Alt-Az context duration of exposure, and number thereof, is the (main?) problem so 150 wins over 130 for photons captured. A secondary problem is the stability of the mount vs. size of scope but you have already proven that is OK for your 150. Another prob might be the focuser (DS vs not DS) but again you have that sorted ! The 130P-DS (if it is like the 150P-DS) has the secondary closer to the primary for photography at prime focus, but you sorted that with your hacksaw. Another prob is criticality of collimation at f5 of the fixed 150 vs the adjustable 130, but you sorted that by un-fixing the 150 ! So I am not seeing why you want to go down to a 130 ? 120 refractors are above my paygrade/competance

CA = chromatic aberration, is what happens in the glass of a lens, like in a prism, and gives the colour fringing that Herzy describes. Does not happen on the aluminium surface of a reflector an Achromat (achromatic) lens attempts to correct this CA for a limited selection of colours by using lens elements made of different refractive indexes. an APO = apochromat (apochromatic) lens, corrects CA for a wider selection of colours by using even more lens elements of even fancier design and thus more expensive than an achromat. The chromatic problems of lenses (refractors) are reduced when imaging through monochromatic filters with monochrome cameras. hth

nice one, glad we kept you awake long enough to catch the clear sky,(I thought it went quiet !!), good start there and yes you deffo need the cut-down focus tube and no barlow for that one, it'll be good to watch how you get on with this target, thanks for showing. (and the late night conversation !)

That looks very interesting thank you, a Live one ,, nice introduction web site etc., only one small problem I dont think my internet is stable enough to take a 2.2G ( or thereabouts ) iso down in one go, nor my browser to recover from a drop. Is there a reliable torrent of it DistroAstro3 anywhere anyone ?

Yes. There are 64bit versions (( windows builds, both portable and installable, of both Gimp2.8 (stable but only 8bits/ch) and the 2.9 (dev with 16bits/ch) The first place that comes to mind is at Partha's Place http://www.partha.com/ ))