ONIKKINEN

I want to observe the sun with a 90mm aperture refractor, what is the way to go? I see there are foil filters, full aperture glass filters, masked partial aperture glass filters, Herschel wedge diagonals, blocking filters at the eyepiece side and so on. As i understand it no kind of eyepiece threaded filter only will do the trick but some kind of full aperture thing (or the wedge?) is needed.

Looking to not spend a fortune but dont have set in stone budget, but around a couple hundred euros or thereabouts would have to do the trick. I see there are a number of options with this kind of budget but have no clue what is the best way to go.

12 hours ago, L8-Nite said:

Consider looking for a Telementor Equatorial mount ?

It can also be used in an Alt-Az configuration.

.

Looks very nice and sturdy, but perhaps a bit too bulky for what i had in mind. When i bring out the big guns i am going out with an AZ-EQ6 and an 8 inch newtonian with all the related astrophotography gear so there is a mountain of stuff to be hauled already. The ED90 on the AZ5 will just tag along for the ride for little to no extra gear to be hauled so i reckon it might actually get used more than the big guy because its easier to handle.

I survived the urge to get another scope... by buying another scope 😆

This one: https://www.teleskop-express.de/shop/product_info.php/info/p11438

Looks right about what i had in mind, and is (suspiciously) cheap. Well see how i get on with it, but since its my first refractor it is guaranteed to also be the best refractor i have ever owned so probably will not be disappointed. I also threw in an AZ5 to complete the grab and go setup. I should be able to stuff all of that into a large backpack and set off wherever, whenever i feel like it without much in the way of excuses to not bring it with me.

32 minutes ago, TheycallmeRiver said:

I can relate to this a little.  Maybe not the manual alt-az, but definitely the feeling that I ‘needed’ a refractor.

I think I’ve been seduced over time by phrases like ‘refractor magic’ and ‘pinpoint diamonds on inky black background’ etc.  Somewhere deep down I felt like I had to see for myself.

Anyway, I’ve owned my dob and my Evo for a while now and I was always intending to buy a refractor at some point in the future, but a couple of weeks ago the WO FLT 132 in my signature came up used.  It was way above my budget but still a bargain compared to a brand new one and I thought why wait?  Thankfully my wife is… open to persuasion when presented with a passionate argument 😊

I drove the length of the country to pick it up last weekend and now I can’t wait to get started using it.  Just waiting on a couple more accessories before I can get going, and I still need to sort out a battery or power tank for the AZ-EQ6 I bought with it.

I think I’m probably set for a while now, scope wise.  Accruing eyepieces and gaining more observing experience are my priorities now.

 

You just described my feelings perfectly with the buzzwords. I keep reading about this velvet black sky with diamond stars and great contrast and punching above their size in terms of aperture. Have no clue what any of this means and these dont really ring a bell when looking through my newt (it is rather fast for visual with a significant obstruction), but that must be the refractor magic at play.

7 minutes ago, Philip R said:

Welcome to the ‘I got more than one ‘scope’ club @ONIKKINEN.

Below are some images of my three ‘scopes.

and two of my three alt-az mounts...

😜🤪

I like the look of these kinds of simple alt-az mounts with 2 scopes on them. Maybe because i want to have the exact opposite experience with visual than with my astrophotography? Pure point and look experience with little to no setup time.

48 minutes ago, Stu said:

Of course it does 😉

Im guessing the black clamp-doodad between the SCT and the skywatcher clamp is some kind of alignment enabling thing? Doesn't look like there is an easy way with the accessories that came with the mount.

8 minutes ago, Wiu-Wiu said:

Why change eyepieces if you can use another scope? 

The AZ-EQ6 i have can be dual scope mounted in AZ mode. Hmm, almost sounds like it needs 2 scopes on it...

3 minutes ago, Pixies said:

And then the next thing you know: 

 

Craziest thing about this video is that Ed seems to have something smart to say about all of the scopes so he does actually use all of them even if just a little bit.

For some reason i have this sensation that i simply must own a refractor on a manual alt-az mount no matter what. Why? I dont know why. I have my hands full with my existing scope and i think it covers most of the aspects in astronomy i need it to, but somehow i still have an urge to get a refractor on an alt-az mount.

I have been wondering why many people seem to have 10 scopes lying around when i have been happy with just 1 and cant think of sound reasoning to own more than maybe 2, at best 3 but now find myself looking for a scope too... Is this how the telescope collection mania begins??

The price to performance ratio of Siril just keeps on getting better.

Looks like there is some learning to do with the new stretching tool. I couldn't make perfect sense of it in a few minutes at least.

8 minutes ago, Rob20236 said:

700 with 1 sec exposure. i need to install siril as i cant see the info your getting in my histogram

2022-06-29_22-32-23__22.00_1.00s_0000.fits 49.49 MB · 0 downloads

This one looks good with a min value of 352 👍.

If you do end up trying siril, just right click anywhere in the frame and click statistics. It will show you mean, median, max, min, etc etc. You can also draw a selection end then check statistics of just that area, for example when checking what kind of background value you have in a subexposure by selecting an area without stars and nebulosity.

3 minutes ago, Rob20236 said:

hows this one looking? i adjusted in increments of 50 until the left edge wasnt cut off at off set 300 (in nina).

as this was only a 5 second sub. will i need to adjust down as the xxposure length increases?

thank you

2022-06-29_22-19-58__23.50_5.00s_0000.fits 49.49 MB · 0 downloads

Still at 0. Try 700?

Also, better to take a bias frame or the shortest exposure possible. Try 0.00001 or something as the exposure time.

9 minutes ago, Rob20236 said:

thank you. so should i keep adjusting offset and checking histogram until the left edge is no longer cut off? start with 100 and go from there?

thank you again

You have enough offset when you dont get any 0 value pixels in the frame. I just used siril and checked the statistics of the frame and it reported the minimum value as 0. Increase the offset until the minimum pixel value is anything but 0, but remember to check this on the gain values that you are going to use the camera in.

In my Rising cam (ToupTek made, as is the Altair) at a gain value of 100 (corresponds to your 200) i need an offset of at least 500 or there will be 0 - value pixels, but since the default in mine was 768 i just left it at there. Your mileage may vary but the 60 offset definitely looks too low.

Thats wild for 60 minutes. The 10 inch f4 is a real beast with mono it looks like.

I sure hope one day i have enough gear. It seems like every other day i am fetching something from the post office or declaring something through customs or just counting my pennies to make another purchase later. And haven't even used the equipment i bought 2 months ago yet due to the bright summer nights!

At least in about 2 weeks planetary season should start and i dont think i need extra trinkets for that. Hmm, maybe i could use a planetary ca... and there we go again 🤣.

23 hours ago, Rob20236 said:

i use nina with altair selected ,not ascom driver. i used sharpcap to do sensor analysis which is in original post.

heres  a "good" dark at 100 gain 60 offset

thank you for any help

2022-06-21_21-45-26__-11.00_180.00s_0000.fits 49.49 MB · 4 downloads

There are pixels with a value of 0 in this dark, which is an issue for calibration as you cant divide or multiply by 0. How big of an issue? Probably not that big, but offset should be increased anyway. There are practically no downsides to having an offset of 500-1000 ADUs with this model of camera as the full well depth is plenty large enough.

Its just a hunch, but it might have something to do with weird patterns, as the sensor probably has some consistency to its readout pattern as to where the cold pixels are situated, and in your case they are clipped to 0.

Below is a screenshot of the histogram, the left edge is abruptly cut off when in reality it should continue as the right edge does.

This is a bit of a MacGyver solution, but thick and soft tape like gorilla tape will do the trick. The felt lining in one of my rings came off and i just put a patch of gorilla tape in there. Seems to be holding nicely and prevents metal to metal contact just as well as felt would, and since its hidden from view no-one will know that you fixed your scope with tape.

Your guiding looks a bit too good to be true, how are your PHD2 settings, specifically the focal length of the guider?

22 hours ago, rpnconsult said:

Hard to say anything about how the mirror is glued from the image. Maybe looks like its a bit off, but you should be able to adjust the position with the collimation screws and the secondary spider screws.

But i see the same issues i had with mine with your spider. The left and right vanes are bent and the bottom vane is twisted so that it presents a larger surface to incoming light. The left and right vanes will produce double diffraction spikes at slightly lower angles and the bottom one will produce a thicker diffraction spike that also appears on the other side.

28 minutes ago, lankywolf said:

Thanks for the advice so far folks... I'm looking to keep things as simple as possible to begin with, which is the primary reason I've been favouring the DSLR/lens rig. I think for me it'll be more about learning and mastering the basics before moving onto more advanced kit. I will read up a bit more on dedicated astro cams, but was of the impression that they weren't really for noobs like me.

I think there are enough things to learn in astrophotography as is and figuring out how to use a dedicated astro cam from day 1 will probably be confusing and lead to some headscratching. DSLRs are plug and play, you have live view, you have a screen to look at, you have the ability to easily view the images (No, you dont have this with astro cams!), you dont need external power or a computer to control it, you dont need AC power or a beefy powertank. With DSLRs your first step into astrophotography wont be nearly as frustrating IMO.

I think your plan sounds good!

28 minutes ago, Dan_Paris said:

For this reason I suggested also clamping levers, which won't have this problem.

 

https://www.amazon.com/uxcell-Adjustable-Clamping-Ratchet-Threaded/dp/B07MXB5L4N/ref=sr_1_2?crid=2VRWVBXD7BHZ7&keywords=clamping%2Blever&qid=1656277683&sprefix=clamping%2Bleve%2Caps%2C157&sr=8-2&th=1

I didn't quite understand what clamping lever meant, probably lost in translation, but this looks exactly like the thing i need, thank you! Fits in the small gap and a lever is even better than a thumbscrew when it comes to handling with gloves.

Just now, Dan_Paris said:

knurl screws and clamping levers are easy to find in hardware store or on Amazon. Don't need to be custom machined.

 

 

I was thinking that if it is the case that there isn't enough space to fit a knurled screw, i dont want tiny thumbscrews that are a pain to use in cold weather. The distance between the hex screw head and the ring looks quite small in the images and i am not sure if a big knurled screw fits there.

If that is an M6 thread, judging from this image there is no room for a knurled screw with a 37mm diameter like TS and hardware store sell. If its much smaller than that it wont be easy to use. That is what i meant by machining the rings so that the connecting bit that sticks out would be a bit longer to make space for a bigger screwhead.

Actually ill ask TS if their CNC rings can fit a thumbcsrew instead of the hex one, and if not, could they machine it so that it can. The only thing about those rings i dont like is the lack of tool- less action. The hinge is not that important, i can just loosen a tiny bit, rotate and tighten again so actually dont need the hinge at all.

3 hours ago, Dan_Paris said:

What about those ?

 

https://www.teleskop-express.de/shop/product_info.php/info/p13075_TS-Optics-CNC-Aluminium-Tube-Rings-for-telescopes-with-235-mm-diameter.html

 

The problem with the GSO/Orion/Skywatcher models is that they have a single thread on top and bottom, which is less rigid.

 

I was looking at these and they look very slick and nice, but they would make the scope a permanent imaging rig without easy tool- less action to change tube orientations.

48 minutes ago, rpnconsult said:

I had recently purchased a VX8 Newtonian that was shipped to me in the USA. I was not able to get much support from OOUK on this so I am posting here

with some questions.

1. Most collimating procedures I have read first want you to position the secondary to be centered in the focuser tube. When it arrived

from the factory the VX8 secondary was definitely not - it was at least 10mm further out from the primary than it would have been if centered. In fact to center

it in the focuser I had to put in longer adjustment screws. Is this normal? Am I missing something?

2. With the modification above, I have it centered the secondary and collimated using a Cheshire. The view through the Cheshire looks good, the crosshairs

are centered on the donut mark and all three clips that hold the primary are visible. No issues with visual observation. Yet when I use a camera

(ASI 294MC Pro), I see that the vignetting is quite asymmetric - i.e. much more vignetting on one side and almost none on the other. So the

"sweet spot" of the FOV is not centered on the camera sensor. Any ideas of what could be causing this? The camera is mounted just

as an eyepiece would be on the 2" focuser.

 

Thanks in advance for any help/pointers.

Sadly, this sounds familiar as my VX8 came with secondary collimation screws that made it physically impossible to collimate the scope properly and i too had to install properly fitting ones.

As for the vignetting part, there are many possible problems and solutions, some free some not. My focuser had a bit of side to side movement as the focuser was racked in and out, so in order to collimate properly you must collimate with the focuser in the same position as the camera will be. Preferably done with a laser as it is easier to place on the focal plane than a long cheshire that probably has your eye be far from it. And on the topic of the focuser, its not very stable, at least mine was not. You will find that the focuser itself sags under the weight of a camera and you will have trouble keeping collimation because of it. Another major source of sag is the thin aluminum tube itself, which can bend and take you out of collimation, and can also bend around the points where the secondary spider is connected to the tube (causing the secondary to wander at different tube orientations.

The focuser issue is solvable completely by changing the focuser, but that costs some money of course. A temporary fix would be to try and adjust the tension screw so that the focuser just barely is able to move in and out and the drawtube is under tension. Care must be taken to collimate under the same tension as the camera will be in. This reduces the focuser sagging effect somewhat, but for imaging purposes you will find that you get annoying mismatches between your flats and lights.

For the secondary, make sure that the screws holding the spiders to the tube are tight, but here comes another problem. The tube itself dents very easily and the spider is lose again, so there may not be a tension that is just enough to keep things stable but also keep the tube round. I fixed this by fitting a heavier and sturdier spider that has an inner diameter the same as the tube itself, so the tube rests on the spider and no further denting is possible. I installed this one: https://www.teleskop-express.de/shop/product_info.php/info/p9317_TS-Optics-massive-Metal-Spider-for-8--Newtonian-Telescopes-D-223mm.html

For the flimsy tube you can get a couple of pipe clamps meant for AC tubing (like below) and so create tension on the tube that will help with the sagging. One between the focuser and finder shoe will strengthen the tube noticeably and may help with some collimation related issues. You might also want to put one more half way between the primary mirror screws and the rear tube ring.

I upgraded to a Baader diamond steeltrack focuser and did the above modifications and found that random collimation issues (unrelated to transporting the scope) reduced to almost 0. The BDS focuser is half of the cost of the scope so its a bit of a stretch to ask, but it is a very good focuser and makes life much simpler. The spider costs a lot of money for what it is and im sure some local machine shop would fashion one out of scrap metal for a 5th of the price, but the one i linked works for the purpose very well.