ONIKKINEN

1 hour ago, Alien 13 said:

No astro gear I know of is designed to be waterproof weatherproof but perhaps damp proof so its best to dry each item as best you can and leave then somewhere warm and dry, sensitive electronics can be placed in a container of uncooked rice if its realy wet.

Alan

Yeah, the mini-pc might have died as it rained directly inside it through the vent holes on top 😭. My tube orientation was such that the camera and the various usb and power ports were also exposed to rain for a bit...

Well ill throw them in a rice bath and hope they didn't mind an unscheduled wash.

As the title suggests, i got caught mid imaging with a quick but strong shower. It took me a while to pull all electronics out and cover the scope.

Is astro imaging gear sensitive to rain, and if so whats the next step?

A simple usb powered dew heater kept my guidescope clear at -20 last winter. Everything else was covered in frost though.

There is probably a "release shutter without lens" option in the settings that you have to enable. 

Thought i would report that i am experiencing something pretty much exactly like this, a colour gradient across the image.

Started noticing this after changing my usual imaging spot of B6-7 to a 6, maybe 5 on the best of days. On the new imaging spot there is an extreme gradient as most targets just skim the edge of a B8 light dome.

Also, there is a baader UV/IR cut filter in front of my camera. 

I am wrestling with IFN at the moment and there is a fine line between fixing the gradient and nuking the nebulosity, but so far has worked out.

10 minutes ago, Dazzyt66 said:

it usually works by the time I get to 100 - I don't think I've ever gone over 200 with it as it washes stuff out.

This sounds like the complete opposite of me. I always crank it all the way right, to 1000. Still the image looks mostly black with some of the brighter stars visible. Probably because all of my signal is within the first 200ADUs or so.

1 hour ago, Tiny Clanger said:

As condensation occurs when moist air comes into contact with a surface that is good at conducting heat (like glass or steel) , I'd guess that flocking would act as an insulating layer, and actually decrease the chances of the sides of the secondary dewing up . As the back of the secondary is facing space, and losing heat , it is going to be colder, and more prone to dew than the front of the secondary.

Heather

Didnt think about that at all. The flocking material is the exact opposite of a reflective glass mirror, so will probably be dryer than any metal/glass parts. Radiation of heat will probably have a lesser effect too when the insides are completely flocked all the way to the top of a dew shield.

1 hour ago, Nyctimene said:

Painting the secondary edge with a black felt tip or paint will still leave some reflexivity, esp. when light hits the mirror under grazing angles. I preferred to flock the secondary's edge (only half of it's circumference can be seen from the focuser) with self-adhesive velour flocking material (D-C-Fix here in Germany). Working in small pieces, I started with making a trapezoidal paper template for the part of the secondary, that points directly at the sky ( - the region of the major axis' exit) and cut it with fine scissors to the correct size and shape. I then transferred the template's outlines with a fine pencil on the velour's paper side, and cut out the part. A small pincette was used to put it into place. The same somewhat fiddly procedure followed with four more pieces (but you have to measure and cut only two templates, that are used back-to-front). The result is shown here with my Skywatcher Heritage 130 P Flextube:

You don't have to work with extreme precision - the main point is just to get most of the stray light absorbed.

Stephan

This looks pretty nice too. I do wonder whether the fibers would attract dew/frost and just bring it closer to the mirror. The backside of my secondary is sometimes wet/frozen, but so far the mirror side has been mostly dry.

I have 2 rolls of flocking and some paint coming soon so plenty of extra material to test and play with.

I use siril, i like the simplicity and user interface. I tend to do background extraction, photometric colour calibration (a blessing, works every time) and a stretch with SIRIL and then move on to photoshop for the nonlinear part of processing.

The background extraction tool works well for most projects, especially if all the data was taken on the same night.

Stretching with asinh transformation first and them the histogram transformation nicely retains colour and i find that sometimes only a minor saturation boost is needed.

Recently switched stacking from DSS to siril with sirilic too. Sirilic stacking allows a background exraction per sub in the stacking process, which is proving to be a necessity for me. Only problem with stacking in sirilic is that it takes about 1gb per sub taken for stacking from my harddrive, so a dedicated SSD is needed.

Hard to beat for the price of free.

I dont think focus is all that important as long as its roughly same. Check this video out, Cuiv makes a few fair points.

I will say that i took flats for a while only after getting back home and sometimes on the next day. I had marked the camera-focuser point with tape to recreate the same rotation and left the focuser as it was when shooting.

Currently i take flats every time since it is pretty easy with a light panel. The dedicated astro light panels are hilariously expensive so i bought a 20 euro tracing tablet from amazon. Works just as well with 10% of the price.

I dont have issues in visual use with an 8 inch newtonian and an EQM35-PRO. The only hassle is making sure the eyepiece is in a usable angle. Different parts of the sky have different tube orientations so the tube rings must be adjustable.

Focusing will take some effort, i will slightly move the reduced 1:10 knob and wait for the shakes to settle over 2 or so seconds and adjust again until in ideal focus. I cannot touch the telescope in any way (including with my eye) or it shakes. But honestly its not a problem at all.

I think the mount ratings are very much accurate for visual use.

9 hours ago, DannyST said:

Thank you, I think this was another error when I was first looking into what I should get. When I planned my set up I looked up the weight capacity on skywatchers website as 9kg and the OTA was 5.5 so I upgraded the EQ3 to the EQ5. Now looking again I see there are posts saying for AP we should not go over 6.5kg. 
 

so this will need addressing, I’ll keep plodding on with my journey and keep an eye out for a HEQ5 maybe second hand but at the moment the ones I see are only just cheaper than new. Could be because of waiting times for new. 
 

thanks

Danny

I am imaging with an EQM35-PRO (basically an EQ3 with extra marketing and an extra counterweight) and an 8 inch newtonian that weighs in at around 9kg with guiding and cameras on top. While it is painful sometimes and windy days are by default no-go it is far from impossible. Shorter subs and leaving DEC unguided are proving to be effective measures for me. I can get around 2/3rds of my subs under 1 arcsec RMS (generally regarded as good) if the conditions are average.

The payload and mount capability conversation has gotten really out of hand IMO. What do you suppose is "good performance" for the payload? Eternal sub arcsec guiding, no effects from wind, never loses a single sub? Looking at 10k mounts there. A more reasonable approach would be: More than half of the subs are good or usable and this you can already achieve unguided, so adding guiding will improve things drastically. In my opinion don't stress about this, its easy to get into a spiral of spending because of general opinions. The EQ5, especially when guided will be quite capable of handling your 150PDS. Wind will keep ruining your exposures but that is a problem that newtonian users just have to live with, regardless of mount used.

The "mount limited" concept is also in my opinion outdated and not quite true. Really there is no such thing as being mount limited, the system is being photon count limited and a better mount allowing longer subs will bring in more photons per exposure. But why not go the other way around and make sure that all photons count? Using modern dedicated CMOS astrocameras you can use exposures as short as 10s and stack 6 of them to get a result that is pretty much exactly the same as a single 60s exposure. I was in the same boat as you, looking for a mount replacement because i thought i had to take longer subs, but changing to a dedicated astro cam changed this completely. I am now looking for more storage space for my computer to allow processing thousands of subs. This applies to DSLRs as well, but you probably cant get quite as short in the exposures, but IMO 30s should be just fine.

Now having said all that i do agree that cheap mass produced mounts should probably not go over 50% of their rated payloads to get consistently good results, but since money is limited for a lot of people i just choose not to follow this argument.

Lots of praise for the FLO flocking material, ill give that a go and see how it turns out. The "ridge" from the crimped part of the aluminum tube sticks out quite a bit and could cause problems, but if the adhesive is as strong as it seems then no problems, or ill just align the seams to the steepest part of the crimp.

4 minutes ago, johninderby said:

This will help.

https://www.firstlightoptics.com/misc/black-velour-telescope-flocking-material.html

Krylon camo ultra matt black works really well. Comes in a spray can but just spray some into the lid and brush it on.

I was looking at these velour rolls, but i wonder how well these handle extreme temperature ranges in terms of frosting and the adhesive? When winter rolls in properly i will have an up to 45 degree difference between inside and outside every time i take the scope out.

Cloudy october has rolled in and i thought why not tinker with equipment in the meanwhile? I noticed 2 potential issues with my VX8, the blackness of the inner surface of my OTA across the focuser (or anywhere else, if it matters) and the rough secondary mirror edge (the marked bit).

How much of an effect do these have for imaging/visual, but mostly imaging. While the paint is very matte and doesn't look all that reflective, it is also very much not quite what i would call black. The secondary mirror edge while not coated, will probably reflect at least some unwanted light somewhere towards the camera, potentially creating extra noise.

I am thinking of just painting these black with something like TS-black or another very low reflection paint. Although im not quite sure how to paint the mirror edge without ruining the mirror itself. Maybe using a marker or a very small brush?

I have this one: https://www.firstlightoptics.com/coma-correctors/ts-95x-maxfield-coma-corrector.html

This one does not quite fully correct coma/curvature on my F4.5, but i would be lying if i said it bothers me. From what i can tell most people would recommend the TSGPU, Explore scientific HR or the skywatcher aplanatic for well corrected fields. The stellalyra 2 inch is quite a bit cheaper than all of these, but i know nothing of the product (nor could i find much really) so not really able to comment on that.

Another thing you should think about is the length of the corrector. If it is long enough to obstruct your focuser you will have an extra diffraction spike, or at least some extra diffraction artifacts. The 0.95 maxfield (sold as both TS and sharpstar, same product) is shorter than most so it probably doesn't obstruct as much, if at all. The stellalyra looks pretty short too, so probably not an issue here.

2 minutes ago, DannyST said:

Thank you, makes me feel better now. I thought I was loosing to many subs, eventually I’ll go guided but I want a better camera first then get it modified.

This was the reason for the 5 mins as my M3 has the hybrid AF sensor and when looking into cameras I saw lots of posts with strange dark lines caused by the hybrid AF. So I was trying to make my m3 do it to find out if it can be avoided. But I never got an image with the dark lines. 
 

now I’m looking for a 600D or a model after the 800D like the 77D etc. 
 

thanks

Danny

If you're planning on getting a new camera and planning on guiding one day, consider not buying a camera for now and getting a dedicated astro cam with the guide setup? Especially true if you're planning on spending more than a couple hundred on a used model.

A cooled, low noise astro cam makes a world of difference compared to DSLRs. The only downsides are price and a bit of an annoyance setting everything up every time, but the results are well worth it. Since you will need some sort of computer to do the guiding, adding the astro cam is no extra effort.

13 minutes ago, DannyST said:

On my attempt at drift alignment, did I get the instructions right? Following a guide but was aimed at AZ mounts so I kind of just did what I could on my EQ Mount. 
 

thanks 

Danny

The alignment is good. I don't see a reason to doubt polar alignment in this. I recommend you try shorter exposures and see where you have a good compromise between signal to noise ratio and failed exposures. The 60s sub in your post looks really good, actually unnecessarily good. If you can see the object in a single sub, then it is a really good sub. The 5 minute sub is actually overexposed, and you gain no useful data compared to taking a 1 minute sub 5 times. Something i would note is that 35 out of 60 subs being that good for unguided 60s subs with a newtonian is actually a decent result.

7 minutes ago, rickwayne said:

I should just know, after all the times I've looked at M31, which way is RA and which is DEC. And on my phone I can't analyze it. But you can. If the trailing is in the RA direction, you've got periodic error or drive train issues. Elongation in DEC, unless you're guiding,  means polar alignment problems. 

The elongation of stars is in the same direction as RA in this case, indicating that the tracking issue is entirely RA related.

Depends on how much you tolerate coma, which there will be a noticeable amount even quite close to the center at F5. I would definitely look into it, but take a few shots and decide whether or not it bothers you?  For very small targets where you crop most of the image away, like planetary will be mostly unaffected.

The full frame camera will have extreme vignetting with the 50mm secondary mirror of the 150PDS at F5 to the point of probably not being worth the effort. The APS-C will have vignetting too, but taking flats will deal with this quite well.

Are you autoguiding?

All mounts experience something called periodic error in RA where the tracking speed oscillates a bit above and under the ideal rate. Unguided exposures are limited by your RA drift rate, which varies quite a lot between different mounts.

Below is an example i just found online, the red line is your DEC, which in this case was spot on as it hardly moves in the long term while the blue line is the RA which is constantly in use. The steep drops and cliffs of the graph are where you experience bad subexposures, but just by pure chance you could have your exposure at the relatively even top section and not notice trailing as much. I don't know what mount (or even if it was a mount) this image is from but it gets the point across. My EQM35-PRO experiences somewhere around 8 arcseconds RMS of periodic error during one worm cycle, which is 8minutes on my model. In theory that would limit a 1 as/pixel resolution image to just 30 seconds, but in reality there are these same steep cliffs and drops in the graph, making unguided exposures not worth the effort.

How much you can get away with will depend on your mounts periodic error and the resolution you're imaging in.

3 hours ago, wimvb said:

I like to leave my calculator in its case when doing astrophotography, but sometimes it has its merits.

What accuracy is needed in the altitude and azimuth bolts to get 10 arc seconds polar alignment?

Suppose that the bolts press at a distance of 7 cm (70mm) from the central altitude or azimuth axis. (For an eq35, this may be an overestimate.) 10 arcsecond rotation at 70 mm, gives 0.0034 mm sideways movement; that's just shy of 3.5 microns, or 1/20th of the thickness of a human hair. Next, suppose the alt and az bolts have a 1 mm pitch (probably coarser). One would need to turn a bolt only 1.2 degrees, 1/300 of a turn, to move it 3.5 microns. With all the friction and stiction present in a coated, cast aluminium mount and base plate, I'd say that's just not possible to accomplish repeatedly. That's why I'm happy enough when I get the polar alignment error down to (less than) 5 arc minutes.

Btw, if your mount's backlash doesn't allow guiding in DEC, you should really consider saving up for a bigger mount. The eq35 is based on the eq3, which lacks ball bearings in the ra and dec axes. In stead it has teflon washers to reduce friction, but those aren't as good as proper bearings. Nevertheless, spending a few evenings/nights getting dec backlash sorted is worthwhile. I got backlash down from 4000+ ms to below 700 ms (at a guiding rate of 0.5) in one night, and it really improved my guiding. But you have to do it in very small steps, and avoid binding at all cost.

I can move the azimuth bolts in increments of somewhere around 20 arcsec, but not much less and not consistently. Sounds about right for your calculations, a 2 or so degree turn doesnt sound impossible. But the take away from this is that any slight bump will move the alignment more than that so not worth the effort trying to go under few arcmin. And of course sharpcap reported alignment is not the whole story.

A better mount is in the shopping list, but seeing as i have some success with the current contraption im in no hurry, not that i could afford one now anyway. Currently with short exposures the effects of seeing and guiding go pretty much hand in hand for high DEC targets so a better mount would be just a convenience purchase, not a necessity.

2 hours ago, ollypenrice said:

I'm willing to believe software said you were within 10 arcsecs but much less willing to believe the software is right! It is incredibly difficult to get as close as that in reality.

Very true, while sharpcap PA is excellent i doubt it is really consistently all that accurate below 1 arcmin, the reported value fluctuates a bit based on which knee is on the ground and what type of ground the tripod is on. I am polar aligning with the main telescope at 0.9 arcsec per pixel so it should be reasonably accurate, at least i hope so.

2 hours ago, wimvb said:

Take a 30 s exposure with trails. View on screen and rotate the camera (eyeballing it). Take a new exposure with trails. View on screen and rotate camera. Repeat until satisfied. It takes about 3 such iterations, normally. All inall less than 5 minutes to ensure camera alignment. Well worth it, imo. If you like spending money, you can of course buy a camera rotator, but really not needed.

Btw, I'm curious why you don't guide in DEC.

Sounds easy enough, shouldn't waste imaging time since the scope will take a while to cool anyway so think i will do this from now on. Rotation is not an issue since the imaging train is not threaded to the focuser, it is clamped with a compression ring.

As for the DEC guiding: I am imaging with an 8inch newton on the EQM35 at around 9kg or 90% of the claimed payload capability. The mount is very much overloaded for photography. I have dismantled, relubed and checked everything but its hardly improvable. The RA is workable, but the DEC axis has horrible backlash and/or stiction problems leading to failed calibrations that sap out imaging time each session. The backlash is also not consistent, there are wildly different backlashes based on which side of the gear is touching. Poor quality manufacturing on some of the parts. I could guide in one direction but honestly not worth the trouble as it requires very good balance, something that is also very difficult with the sticky mount. I dont want the DEC axis doing anything at all during operation to reduce the chance of failed subs with the once a month type of weather im getting.

Not guiding in DEC is a minor issue with good polar alignment and short exposures. I am shooting mostly broadband targets from light pollution so 30s exposures with the 8inch aperture are more than enough, and short enough to make DEC drift a non issue. I would take shorter subs if i had more storage space, but processing a thousand subs is a bit of a pain already so probably wont. Now dithering is something i cannot do in DEC, but i don't really see walking noise with the low noise IMX571 so its all good.

59 minutes ago, wimvb said:

Generally, I'm pleased when I get it lower than 5 arc minutes. But I always try to have my camera sensor aligned with RA. This makes framing between sessions easier.

5 arcmin is probably always fine, but as i don't guide in DEC i want it to be as good as possible so i don't have to babysit the guidegraph. Aligning sensor with either 0 or 90 degrees to RA sounds really foolproof, think ill try that next time. How do you align it, is there an overlay in sharpcap or some other software? I dont think there is one in NINA.

Below is what i usually get when things go right, maybe polar alignment is one of the strong points of the otherwise weak mount? Who knows.

I am certain that it was under 10 arcsec when i did it, and when i started imaging. Getting accurate PA is no problem, since the azimuth screws have quite tight threads (M5 or M6) on the EQM35. The altitude bolt however is quite sticky and its difficult to tell whether its just stuck or well secured.

However now i have my doubts and checked the guide logs, and it varied from 1 to 12 arc MINUTES between guide sessions... I did not start guiding straight after PA, as i did some tests with snapshots on various targets due to weather conditions. I started the actual sequence and imaging after about an hour since polar aligning. The tripod must have sunk or the altitude bolt was not properly secured. It was also windy so i had to babysit the telescope every now and then, which is also why i didn't pay any attention to drift. With 30s subs most shots were between 0.5 and 0.8 arcsec RMS anyway.

I was also shooting towards 74 degrees or so in DEC, does this have a greater or smaller effect on the rotation with polar alignment issues? I might have to re-check the polar alignment from now on after a while once the mechanical parts settle after a while.

I captured some data about a month ago, marked down both the camera orientation relative to the focuser and the Newtonian OTA relative to the tube rings and still had an 8 degree rotation between sets yesterday.

In both cases the polar alignment has been pointlessly good, at below 10 arcseconds as it is pretty easy to do with Sharpcap pro and the small adjustment screws of the EQM-35PRO. Both sessions have also been pointed entirely by plate solving, to 30 arcsec accuracy. I am not guiding in DEC so it drifts a bit before i re-center, but never more than lets say 45 arcsec from the image center. In both sessions the platesolver has reported an image rotation of around 77 degrees, confirming that everything was where it was supposed to be.

What can cause this? First session i got 2h, yesterday i got 3h. I am planning on capturing a lot more and cant really take a big hit on rotation for cropping.