bomberbaz

With John here in the main, the filter has limited use. I have the identical list to what Don posted but I have either struggled or not needed the Hb filer with them. EDIT; The key to nearly all HB targets is very dark skies, moving on. This is my opinion and not fact btw. Where no comment, I have not yet got around to trying with an HB. I used a 14" F5 dob and eyepiece giving a 5mm exit pupil: 1. IC 434 w/B33(HORSEHEAD NEBULA) Absolutly needed2. NGC 1499 (CALIFORNIA NEBULA, naked eye and RFT) UHC also works, not a huge difference between the 23. M43 (part of the Great Orion Nebula) Need to try this again so no comment4. IC 5146 (COCOON NEBULA in Cygnus) difficult, I wasn't sure if I saw.5. M20 (TRIFID NEBULA, main section) 6. NGC 2327 (diffuse nebula in Monoceros) 7. IC 405 (the FLAMING STAR NEBULA in Auriga) UHC works fine for me8. IC 417 (diffuse Nebula in Auriga) 9. IC 1283 (diffuse Nebula in Sagittarius) 10. IC 1318 GAMMA CYGNI NEBULA (diffuse nebula in Cygnus)11. IC 2177: SEAGULL NEBULA (Diffuse Nebula, Monoceros) 12. IC 5076 (diffuse nebula, Cygnus)13. PK64+5.1 "CAMPBELL'S HYDROGEN STAR" Cygnus (PNG 64.7+5.0) Superb with the HB, jumps right out at you. Very difficult without a filter. Not tried a UHC though, suspect it will do well on it.14. Sh2-157a (small round nebula inside larger Sh2-157, Cassiopeia)15. Sh2-235 (diffuse nebula in Auriga).16. Sh2-276 "BARNARD'S LOOP" (diffuse nebula in Orion, naked eye)17. IC 2162 (diffuse nebula in northern Orion)18 Sh2-254 (diffuse nebula in northern Orion near IC 2162)19. Sh2-256-7 (diffuse nebula in northern Orion near IC 2162)20. vdB93 (Gum-1) (diffuse nebula in Monoceros near IC 2177)21. Lambda Orionis nebular complex (very large, naked-eye)22. Sh2-273 "Cone" Nebula portion south of cluster NGC 2264 The objects that respond are limited and the objects that only respond to HB are even more limited. You will get a better response using equipment which gives a large exit pupil at 5mm or close too that, these are very tight band pass filters and you need to let a lot of light hit your retina. I think a slow (F6 or slower) will struggle on nearly all of those objects but I would be interested to hear how you get on. Dispite all my perceived limitation of the HB filter, I won't get rid of it. Steve

Sounds perfect if I am honest, a lot of thinking to do and probably gear to be moved on if I do decide to go ahead. Thanks for the response though, I know enough now to make a decision.

Is that an ST4 to USB cable Elp? And what about alignment, any change to that process?

I have my eye on this mount, lightweight, apparently tracks very well and excellent capacity so really peaking my interest. I have found a very useful thread on CN regarding it but wondered if anyone on here has a HEM15 that they use with the ASI air plus. Anybody own an iOptron HEM15? - Mounts - Cloudy Nights There is mention to connecting the air+ in the thread but I wasn't 100% what the contributors were referring to. So in particular I want to clarify how do you connect the Air+ to the mount ie USB to ST4 cable / ST4 cable / a.n.other cable Is the setup process to polar align the standard way using the phone/tablet app. Anything else really. EDIT As per title I edited, this also refers to the HEM27 & CEM28 users as apparently the mount protocols are the same. A purchase isn't imminent but just doing my homework.

There are times I miss the mak for the moon. The compact size had a lot to be said for it. Fitted perfectly on the little az gti which allowed you to really relax at the eyepiece at very high power (+250) and really tease out minute detail along the mountain ranges, craters or channels.

I bought 2 of 8mm bst for using in large bins. They are top end of what is useable in them, so don't get used that often and so didn't want to sink a lot of cash into the pair.

Yep read it, identical problem in every way. I am wondering if there is anything in common with our gear which identifies why this is occuring!

I have somehow managed to replicate your problem, solved it in the identical way. What are you using by way of controller to capture the imaged. I am using the ASI Air+ Steve

Good utility this, is there a key to the light areas or am I missing something?

My initial stack with the now good darks with no processing is coming in at 173MB, that's around what I would usually expect. However this effort that my initial post was about, with the apparently dodgy darks shrank to 6MB. (see attached) I have never come across this before, I hadn't done anything different to what I normally do and it was very strange.

Sorry but I am not sure what you mean. I just screwed it onto the OTA and used it as it was out of the box, I have not tinkered with anything purposely since then. Can you elaborate please?

I have actually now managed a half decent effort for around 75 minutes. Far from enough but promising.

I am at a loss with what I am doing wrong but something isn't right, I have been stacking some data of the cocoon nebula just to try and see how it's looking (I know there isn't yet enough) and honestly my results so far are awful and strange. Equipment: 72ED ota, 183MC Pro and Askar DB Filter. Data. 45 x 2 minute lights, 32 2m darks, 32 0.2 flats/dark flats Stacked in DSS and here is the first noticeable issue, the TIFF files are only around 6 (six) MB, hmm this does not look right. In FITS they are 236 MB but the quality of either is absolute pants. I downloaded and installed the new version of DSS as I thought maybe there was a file corruption but this didn't change anything. I have attached the Autosave TIF stack and one each of files used. If someone would be so kind as to have a look and see if it is something glaringly obvious that I can't see for looking I would be very grateful. UPDATE: I did a bit of playing around stacking lights only, the lights/dark, lights/flats etc, and I found that when I omit just the darks from the stacking process, the file size goes from 6MB to 174MB which is where I would expect it to be. So it appears that there is an issue with the darks, although I do not know if it is one or more or indeed all of them. On the face the sizes are fine, looking through them I see no visual corruption. I have also attached the masterdark tif. After retaking the darks, the issue is sorted and the image is now good, albeit grainy. I will post this anyway in case anyone else has this problem as it could be a good reference for trouble shooting. Steve Autosave.tif Light_IC5146_120.0s_Bin1_183MC_gain115_20230824-222350_0001.fit Flat_200.0ms_Bin1_183MC_gain115_20230825-132945_0004.fit Bias_200.0ms_Bin1_183MC_gain115_20230825-133412_0001.fit Dark_120.0s_Bin1_183MC_gain115_20230825-095455_0001.fit MasterDark_Gain115_120s.tif

Some good points made there Paul although what you said doesn't surprise me. Visually I use a 14", moving up from a 10 from three years since. My difference was immense and immediately apparent although like you I would struggle to actually say what those differences are right now. (It's an age thing) I think I have already decided that an F4 by 8" will end up being my scope should I go ahead. It is the balance between weight and aperture, ease of set up, matching with a decent mount and having thought about it, the quattro (which is what I was looking at) seems to meet all the requirements.

actually you have thrown a new consideration into the mix Peter, physical capability! Having just turned 60 and suffering from carpel tunnel in both arms (which has led to muscle wastage) maybe the 10" is less of a good idea. However I would still like to hear other comments if there are any regarding the merits as per initial query. cheers, Steve

I am doing some forward thinking as at some point if things progress, I may upgrade from my fairly basic setup to something more advanced. Putting aside slit spectroscopy for now, I am more concerned with the merits of reflecting OTA's as per the thread title. They are similar priced, they 10" will have a better resolving power but the F4 helps gathering data and should give a brighter image but that's where I lose it. I do not know if the F5 10" will have a significant increase in resolving power over an 8" OTA at F4 with regards spectroscopy. I don't think I have ever got my head fully around how F ratio works and I have simply learned to accept the merits of slow/fast and how best to exploit them.

I use Siril to do the main work, there is a process which is largely automated and does 3/4 of the work. I then use gimp to finish things off. My siril process is below if you want to try it: 1. In Siril apply Colour calibration. A From the top, select Image Processing > Color Calibration > Photometric Color Calibration. In the window which appears, select the "Image Parameters" box, type in OBJECT DESIGNATION and click Find. Some options should appear underneath after clicking Find. Select Simbad OBJECT NAME (or NED OBJECT DESIGNATION if you don't get that option). Then click OK. Wait for it to complete and click close. The bright green RGB picture should disappear and be replaced with something looking better but suffering from gradient. The Crescent will be in the centre against a greenish/black night sky and framed by reddish clouds. B Select the Blue Red or Green channel but not the RGB channel. The Siril background tool dither option is there to dither the background samplers, leave this unchecked. On the topic of the background tool, make sure you have cropped the incomplete edges, dont place too many samplers and that none of the samplers are on stars or nebulosity. Put the preview mode to Histogram and negative to get the best view on faint stuff. Dont trust the automatic sampler placement! Select Image Processing > Background Extraction. Use these settings in the window which appears: Degree order 4; Samples per line 20; Tolerance 1.00; leave Add Dither unchecked. Click Generate. A load of small green boxes will appear. Right click on whichever green boxes touch or are very near to the Crescent nebula to make them disappear. (You can't get rid of boxes if in the RGB channel, hence changing to one of the others). I got rid of 4 boxes. You don't want them touching your target as that'll make the program think it's part of the gradient. Click Apply then Close when it's finished.

I spotted this advert for a moon filter that implies it enhances the view of the horsehead nebula. I have seen some rubbish and misleading adverts before but this is the worst I have seen in some time. Needless to say I have reported this advert to amazon but if anyone else wants to follow suit, it may force them to act. Telescope Filter, Moon Filter for Astronomy, Telescope Eyepiece Standard 1.25 inches Filter Accessories,Thread Pure Optical Glass Lens Reduce Light Pollution: Amazon.co.uk: Electronics & Photo

It could actually be a parrot !

I have emailed the seller to ask the serial number, if it is a post 100K I might just go for it, cheers for the info.

An interesting topic this, I was looking at a second hand one recently. I have a query, is the front etalon rust problem only with older models? And does anyone have a diagram of the inner working which show where mini ITF filter lays?

Anybody who missed this, get it on catch up. Some great contributors, excellent science fact, theory and graphics. One of the best episodes in quite some time imho. Steve

This popped up on my PC browser whilst I was looking into a different matter and it seems very interesting. Not sure if this is old news or not but certainly a beautiful apparition. Rare 'Einstein cross' warps light from one of the universe's brightest objects in this stunning image (msn.com)

That's pretty impressive for 3 mins unguided, a real confidence boosting snap!

I think all in the UK feel your pain atm John, just to be able to do some garden double hunting would be nice but alas, the cloud gods do conspire against us!