ollypenrice

Vlaiv has it nailed for you. Regarding your question 4, as well as the extra step of having to polar align an German EQ mount, you have the added complication of the 'meridian flip.' An EQ mount has counterwieghts one side and the scope the other. Once it tracks to the meridian, or shortly afterwards, it will have to swap sides by doing a 180 rotation on both axes. It is a time consuming palaver you don't need except for long exposure photography. An EQ mount will also put the eyepiece at a greater range of heights than will an EQ. Moving just side to side and up and down a tracking alt-az mount behaves in a more logical way and will provide better Go-To accuracy in most cases because the 'flip' requires both good polar alignment and more accuracy in the star alignment and mechanics of the mount. Don't turn visual observing into a computer exercise... Olly

Lovely job and what an improvement! Before doing anything else it is vital to get the background sky right. Lots of colour in the galaxies, too. Very classy. Olly

Fabulous piece of work. Cassiopeia will never look the same again. And that, I think, is the whole point of deep sky imaging; when we look up we see the Big W but when we look at your image we see what's really up there. The craftsmanship of this image is exquisite. Perfect. In this kind of project you're in a class of your own, Tom. Olly

A very nice Crab and an enjoyable write-up, Steve. Jocelyn Bell Burnell, who discovered the first Pulsar, tells the story of a woman pilot at an outreach event in the early fifties who said she could see the nebula flashing. When told it would be scintillation she said that she knew about that, and that she was detecting something different. Jodrell Bank's one year Introduction to Radio Astronomy Course gives you the data from a lunar occultation they observed. This gives two possible locations for the pulsar, only one of which is plausible on other grounds. Very cute! I'm still waiting for RGB for ours. Terrible weather all over Europe this winter! Olly

There is no real need for fine temp. control of dewheaters unless you are trying to preserve battery life in the field. Olly

Andrew can be relied on for the physics and experimenters will confirm that more weight on a shorter arm is the better way to go. There is no doubt about this in my view. How much difference it makes will depend on how close your system is to its limits of performance. My own system is not under any significant stress from this issue but anyone wanting to refine their autoguiding should pay attention to the physics and use more weight on a shorter arm. Olly

This is a probably a microlensing artifact for which many of the present CMOS cameras are well known. Alnitak itself is very good and sweetly split. There is no clean (some would say 'ethical') way to repair this but if you learn Photoshop's arsenal of brushes you can get it to look like this: You might well prefer the honest artifact, though this was done with just a screen grab and could look better if done with a TIFF. I made a copy layer and initially worked on the bottom, using Curves to get the diamond-shaped artifact flattened out into a uniform brightness. I used the eraser to make a 'hole' in the top layer and then lowered the brightness of the bottom layer till it all looked seamless but very flat. I flattened that and then put a circular selection around Alnitak, feathered the selection and brightened it to give the star a more spreading glow. None of this has anything to do with astronomy, it's all graphics! Awe c'mon, that's a good Alnitak and a dead easy cosmetic fix if you felt like doing it. It's a bit blotchy from the cloud but you could shoot more data or just noise reduce the bright area. If you wanted to hold it down you could just make a gentler stretch of the same data and either layer mask it in properly or just paste the gentler stretch underneath and use a feathered eraser to take the top layer off. Proper layer mask tutorial is here: http://www.astropix.com/html/j_digit/laymask.html Jerry Lodigruss is very good and a nice guy! Here he uses different exposures but it will work with different stretches as well. Olly

You could just put typing paper in front of it. Many of us do that. Olly

Could you not just stand the light source at right angles to the lens and a small distance away from it? Do you really need to attach it? Olly

To step back for a moment, LRGB is faster than OSC because an OSC camera always has a colour filter in front of every pixel all of the time. When shooting in luminance a mono camera is recording all three colours simultaneously, thereby catching roughly three times as much light. And then, as said above, it uses every pixel for receiving narrowband filtered light. It may be more frustrating in on-off cloud cover but mono is faster. The Baader filters are very good. I use their LRGB and OIII and sometimes their Ha, though I also have an Astrodon. The OIII is the least convincing. Some examples produce halos but it seems that Baader will replace ones that do. There has been some discussion on the forum about halos and reflections from the ZWO filters. Indeed there has been discussion about this, and about microlensing artifacts with some CMOS chips. I'm not up on this discussion since I use CCD for the present but you might want to look into it. Filters simply have to be large enough not to vignette the chip (mask off its outer edges.) Mild vignetting can be cured by flat fielding but you should take the manufacturer's advice on which size to use in which system. Basically larger chips need larger filters but the distance between the filter and the chip also comes into it. A filter which vignettes when further from the chip may not do so when positioned closer. Filters need to be 'large enough' but there is absolutely no virtue from being larger than 'large enough.' Olly

Hi All. Witch Head Nebula, HaLRGB, Tak FSQ107/Atik 11000/Mesu 200. Comet Iwamoto in the Flaming Star region. Comet imaged with guest Anne van Houwelingen in our TEC140/Atik 460. Background image Tak FSQ106/Atik 11000. Mounts Mesu 200. NGC7331 and Stephan's Quintet, HaLRGB, Dual TEC140/Atik 460/Moravian 8300/Mesu 200. Imaged with guest Dave Boddington. IC348 extended to include NGC1333 with guest Paul Kummer. HaLRGB. Widefield mosaic, Tak FSQ106/Mesu200/Atik 11000. High res sections Dual TEC 140/Atik 460/Moravian 8300/Mesu 200. ...and finally NGC1333 from the high res contribution to the previous image, also with Paul Kummer and the dual TEC140. Special thanks to the co-owners of some of the kit used here, Steve and Elisabeth Milne and Tom O'Donoghue, as well as to the guests credited above. Thanks also to Rob for the thread and to all at SGL and FLO. Olly

It's not a difficult one to do but you can make it easier to perform by first rotating the image so that the trailing is vertical or horizontal. That way you only have to operate the move function in one direction. Copy layer. Blend mode darken. Filter-Other-Offset. Make the offset a point too much rather than too little then you can go to Edit-Fade -Fade Offset and get micro control over the amount of offset. Flatten and de-rotate. Olly

Great stuff, Dave. I thought that M27 and M33 were getting a bit bright towards the cores and might benefit from a gentle easing down of the upper brightnesses. Tremendous Quintet. Olly

I think it's great. You have that brown IFN colour, too, which is good going. I reckon a little noise is allowed in IFN images! Olly

Yes, Adam Block and Warren Keller can certainly be trusted, as can Robert Gendler. The book Lessons from the Masters is helpful once you've found your feet. Olly

I don't know, but how might you 'test this test?' How about putting your test star in the corner of the image, trying the B mask, getting focus perfect, then turning the B mask through 90 degrees and trying again? If the star is defective in the image but looks good in the B mask in both orientations then I would suspect that the test were useless. In truth I don't think it will prove to be a valid test but I don't understand the optical principles of the B mask well enough to be sure. If you find that one corner or side shows elongation you could try rotating the camera through 90 degrees to see if the elongation relocates itself on the image or follows the camera. Chips tilted within the camera are not unknown. I admire perfectionism in imaging but, trust me, we have seen a lot worse! Olly

I would recommend Steve's 'Dark Art' book. There are indeed some first class Photoshop video tutorials out there but there are also plenty of examples of utter gibberish in which ambitious beginners thrash around murdering their data without the slightest clue what they are really doing to it. A really simple rule to follow in learning image processing is, 'Don't, ever, do anything you don't understand.' It isn't about clicking, it's about understanding. Olly

You're in the Observing section. Mods might care to move you to imaging. Olly

But is it? If it were, an f8 telescope of any aperture would be slower than an F5 telescope of any aperture. But my neighbour's F8 telescope saturates his chip in anything over a couple of minutes. It looks like this: It's an 80cm F8. It's fast. Olly Edit: More on Marc's project here: http://www.obs-bp.com/album-1774976.html

I love it! It certainly isn't brassy. This is more oboe than trumpet, methinks... Really good image. Olly

Being a pragmatist, I would do the following: Make two different stacks from each night. Align them in whatever software you use for this. I use Registar. Open one in Photoshop (or other program with Layers) and give it a basic stretch, far enough for the noise to be creeping into vsibility but not much beyond. Open the second stack and stretch that in the same way, getting the background to the same values as the first. Paste the second onto the first and then use the opacity slider to find out the weighting which gives you the lowest noise. (Just zoom in close and use your eyes.) Flatten and continue to stretch. This approach is often called 'stacking the stacks' and is, theoretically, less effective than stacking all the separately and previously calibrated subs. However, in many practical tests I've found precious little difference between the real results. My own stacking program, AstroArt, would allow me to calibrate but not combine all my subs so I'd have a complete set of subs, calibrated with their own darks/flats etc, which I could then combine as usual. In situations where the Sigma clipping of outliers were important (eg where many satellite trails were present in the subs) this method would have a significant advantage. Olly

On the other hand it might make it better. Damian Peach has done some very famous high res. planetary imaging from Barbados, which he chose for its seeing rather than its transparency, which is not particularly good. Haze and good seeing often go hand in hand, just as do high high transparency and poor seeing. (Yet another astro-hassle!!) Olly

Some time ago I had a group of experienced imagers from a UK astronomical society here. At home they operated under light polluted skies. As they were setting up their equipment they had to ask me to confirm which star was Polaris because, with so many stars on view, they were no longer sure they'd got the right one. And it's perfectly true that your first visit to a very dark site can leave you disorientated. Olly

Be careful what you wish for; I ended up emigrating! 😁lly

As high in the sky as possible, wide field EP and an OIII filter. Start by spotting the naked eye triangle marked 1,2,3 below. Star 3 is the one with the WItch's Broom running right through it. Try moving that star just out of view if you can't see anything. Apologies for the digression. Olly