ollypenrice

I wouldn't expect any software currently available to be able to sort out a big mosaic by throwing the raw data into the pot and pressing 'Go.' I think that, as things stand, mosaics are partly automated, partly hand made. I had the great good fortune to be invited to play with Yves Van den Broek's 32 panel extravaganza around Cepheus. https://www.astrobin.com/g82xf7/B/?nc=user Let's look at the software: Yves tried combining the lot in APP. In some was the result was superb, in some ways not. APP did give a geometrically coherent picture. Because he'd used plate solving and a mosaic maker I felt that the data ought to be pretty 'true to the sky' and the output mosaic was almost oblong but not quite. Rightly or wrongly (I'm out of my depth) I used Ps to remove the slight distortion and made it oblong. This was a small adjustment but let me keep some nice bits in the final oblong crop. Once I had this geometric template I had to make each panel fit it seamlessly. Ah! The fun bit. 😁 I used a combination of Pixinsight, Registar and Photoshop and got as far as I got. You can see the image. Starting again I could do better but, hey, 32 panels!!! The day will come when the highly stretched astrophographic mosaic will be a one click affair but we are not there yet. Or, at least, I'm not! Olly

Very, very nice. One thing about this target is its enormous size. Mosaic would be good... 😄 Olly

Wow, when I saw this image I didn't think, 'portable setup, camera lens.' Not at all! Very impressive! Olly

Image scale arises from pixel size and focal length as Merlin says. You have no realistic hope of resolving detail at 0.74" per pixel because, ignoring the seeing, your mount would need to deliver a guide RMS of half that, so about 0.35 arcsecs and an autoguided EQ6 is unlikely to provide that. And then the seeing will get you as well. Now with a CCD camera this would matter because this oversampling would cost you signal in relation to noise. You could hardware bin to mitigate the problem. But with a CMOS camera is oversampling such a big deal? I would have thought not. Read noise is very low. If you over-sample, at least your results will be at the limit of your equipment and the sky. I wouldn't morry about it myself. Olly

Don't underestimate the power of Penrice's equation, S/A=V. (When S = southness (??) A = altitude and V = verdance (???????) 🤪lly

Mars sometimes moves retrograde, sometimes like the other planets. Polaris won't cross the EP at all... Olly

I still use ST4 on both setups. ST4 cable camera to mount, USB camera to PC-PHD2. I don't fix it cos it ain't broke... Olly

Agreed. Olly

But the sampling rate's not the same? Olly

So would I, but Mak plus Canon plus much more exposure time. Olly

How about de-starring the low res data in Starnet++ before combining it? That might let you keep the smaller stars of the original while exploiting the Ha signal. Olly

More data would always help. I think the weakest part of the image is the dark dusty region from the Gulf of Mexico to the Pelican which looks slightly black clipped, though it just may not have enough signal for the very faint parts to be showing. Stars are nice and tight. How about a short run without the filter to let the blue stars show? These filters kill the broadband blue. Olly

You'd be hobbling yourself trying to do Hubble Palette false colour with OSC. The Ha would be captured using a quarter of the pixels, the OIII with half and the SII with a quarter. Given that mono imagers usually find the SII signal very feeble anyway, dividing it by four wouldn't be a good idea. An OSC camera is best used as an OSC camera - that is a broadband natural colour camera. You can enhance Ha and OIII signal quite succesfully using filters but, at some point, you have to say, 'Why did I choose an OSC?' Olly

Yes, that's more or less what a lot of us do. In my case I add Ha to the red channel and OIII to the green and blue channels using blend mode Lighten. That way the narrowband data only ever adds and never subtracts. Olly

I endorse all this as a provider. Debugging and fixing is a non stop operation. A remote setup with nobody on site? 'Not a chance,' would be my view. Olly

As a robotic host (with no availability) I rather dream of having someone else fiddle with my kit! 🤣lly

For the Horsehead you don't need any narrowband filter, though Ha will add to the structure seen in the cloud behind the Horse. The HH itself will be unaffected. Be aware that a duo band filter will block the broadband blue so it will spoil the lovely blue reflection nebula lower left of the HH. (That's NGC2023.) It provides a wonderful colour contrast with the Ha and, if you go for a wider field, with the yellowish colour of the Flame. This region suits any focal length, longer or shorter. BTW this thread would be better in the Imaging Discussion section. Olly

The way to cut the cost of a robotic setup is to share it with other imagers. Would that work for you? Olly

Let's think of some useful items: Dish washer. Vacuum cleaner. Pan scourer. Umbrella. Wheelbarrow. Now let's think of some useless items: Penny farthing bicycle. Photograph of Brigitte Bardot in 1961. Caterham Seven. Hang glider. Observatory. Need I say more on the subject of usefulness??? 🤣lly

Why give up? Why not do something else until clear skies return? Olly

Sorry! 🤣 I said this because it's often assumed that round stars mean good tracking but, when calibrating our first Mesu 200 in PHD, we had round stars from the start. However, they were rather large round stars and, as we refined the guiding parameters, they got smaller as the errors reduced. As I'm sure you know, as long as your guide RMS in arcsecs is half or less of you image scale in arcsec per pixel, your tracking will be perfectly fit for purpose. Relax! Olly

Hmmm, PI just refused to open it for me. I closed it in PI but then AstroArt wouldn't let me rename it because it was still open in PI - which it wasn't. Other members might prefer not to download it till this is resolved. Olly

For some reason none of my programs will open your TIFF. Odd. Olly

Greetings. The camera will fit the scope but the basic EQ5 would leave you a little 'under-mounted' for an 8 inch scope. Deep sky imaging is all about the mount. It must track with extreme stability and precision over the long exposures needed. Olly

You over-estimate the imagination and vocabulary of the average disruptive child, I'm afraid, Andrew! I always enjoyed teaching those kids capable of calling me (with some justification) a half mummified fossil. They were the good ones! Olly