irtuk

Don't go chucking the coordinates of a mountaintop Chilean observatory into clear outside... the heart aches

nice one. I have this tonight so not really a great astro night. Mark 1 eyeball observations also confirm its a miserable solid blanket of thick low cloud down here

That's a great moon pic slaine, welcome to the forums and welcome to Astrophotography. hopefully you can get some nice dark skies down there in Wiltshire.

I was just sending a pic to my dad, yes, don't be fooled by the beard I'm not Santa's grandad, and I said "this is Hydrogen Alpha data" and I was then going to explain what that was when it occurred to me that I don't know. I know that its "light" at a particular wavelength of 656 or so nm but is is emitted by hydrogen or filtered through hydrogen? so in a HA sub, is the recorded signal starlight that has passed through a region dense in hydrogen, or light that has been emitted by hydrogen ...erm ...doing something? I want to say combusting but my knowledge sort of hits a brick wall after the spelling of "Hydrogen" and I am certain combusting is not the right word. Ed.

Changed search defaults. I'm sold!

Thanks, I'll have to give that a try.

also its apparently quick and easy to protect hubble...

Cheers Steve. Thanks for the input though, I went out and measured the optical train and it was already pretty close to 49.2mm so it would have been when I took the sub. I am going to experiment with some very small spacers, see if I can fine tune it, but it really is just the corners.

Yep. we should be good to go. At this point my wife walked in from work and said she had managed to get tickets to a show in Canterbury this evening. Both "Yay" and "Doh" Ed.

So lets see if I have got this right.! By my calculations I need 55mm of back focus PLUS 0.7mm of filter allowance for a total of 55.7mm I then subtract the 6.5mm of back focus that's provided by the camera itself between the edge and the sensor and I come out with 49.2mm so the distance X in the picture from Tooth_Dr should be 49.2mm?

Great thanks. solid advice there. I did wonder what those discs were for. I think I should also check to see if a snail has taken up residence in my scope from that picture. Ed.

Righto. thanks. I will see what I can do with the baffling array of rings and gizmos I have in the box I don't understand the statement about spacers as 1/3 the filter thickness, the filters are these ZWO 1.25" Ha SII OIII 7nm Narrowband Filter Set | First Light Optics and it says the glass in the filters is 2mm +/- a very small amount so 1/3 that would be 0.66 Is that what these mysterious fellas are for? they are about half a mil thick each Ed.

I just took another measurement and its 51mm from the front of the thread to the same position. is this the measurement we think should be 55mm?

ahha. this has come up before some time ago. I used the 61mm from the manual here's my imaging train, bit tricky to photograph with one hand but should give you an idea: I recall when I set it up it was 61mm from the front of the flattener to the little black nubbin on the camera which I am assuming indicates where the sensor is within the case, that's on the underside of the camera in this shot

Here's a single HA sub, 600 sec, guided IC1396_LIGHT_2021-10-17_22-40-13_HA_-10.00_600.00s_139_0006.fits it really is just in the corners so I am not that bothered but if its an easy thing to diagnose and fix then why not, I certainly have bigger problems to address

its a snippet of the corner of the stack. the stars are lovely and round in the centre and quite a way out to the edge. its just at the extremities I get the eggs.

First light on my new Esprit 80 ED yesterday in a brief cloud break. I have the dedicated field flattener for it as well. It's Quite a large image, and this is right in the corner. is this par for the course or can I improve my back focus from camera to flattener, or anything else? some slight egg-shaping on stars going on Ed.

I went out to have a look and identified that one my daughters apps on the tablet had possibly updated itself and opened, then shut the screen off, so it was struggling to take a flat of Disney Princess Hair Styles, which I can totally understand.

It seems to be struggling with the S2 filter, needs a very long exposure.

Nina is managing it all. and yes its taking between 4 and 6 second exposures on the HA filter, balancing everything out. I am in a meeting

ok so yet another idiot question I think I already know the answer to but here we go... I am using a tablet flat frame app with the HA filter and the flat looks darker than I expected at first, however this is because my tablet produces very little Hydrogen Alpha signal. Right?

Sounds like an overwhelming vote for separate then. Its not much of a chore with the NINA wizard. Thanks all for the input.

Clue in the title I am running off a new set of flats using the flats wizard on NINA and its got options to do flats for each individual filter. Is this worth it?

Thanks for the advice Michael. I am a bit restricted on what I can calibrate on because of the location, but the setup is permanent. I found another candidate for the source of the problem as well, camera not tightly screwed in! I think over time its become a bit loose. The whole rig needs a reset now anyway as I have just received a new scope that I need to get dialled in, and I will be doing this with the benefit of lots of learning Ed.

Good point, I will see what I can do, maybe take some weight off it, I think its probably just a snag because I have not had the same issues on other targets. when the interminable clouds clear I will give it another go.