markse68

12 minutes ago, Second Time Around said:

I've got one of the "posh Russian ones" in black.  I hope to do some solar observing before long.  I had the idea of putting a foil cover over the top (as in the frost protectors for windscreens). 

Anyone tried this?  If so, did it work?

So that you cook through more evenly without going too crispy on the outside? 🤪

Fancy Russian what though- is it designed for this purpose? Is it insulated for the Siberian winters?!? Must be baking in there if it is! Where did you get these half stitched pillow cases? 😉

14 hours ago, Louis D said:

The real acid test is to remove the mirror an put the tube at a shallow angle to the sun and see how bright the tube wall looks.  I've yet to find a flat black paint that doesn't look shiny at shallow angles under these conditions.  Perhaps if there was one that sprayed actual 3D particles forming tiny light traps it might work better.  I'm thinking along the lines of the fake hair sprays of the 80s/90s.

Gerd Neumann recommends just blackboard paint and suggests mixing it with sand for that very purpose- but obvs brush on. I guess you could do that with the black 3.0 too for ultimate solution? 

https://www.gerdneumann.net/english/instrument-building-parts-teile-fuer-den-fernrohrbau/totmatte-schwarze-optikfarbe-deep-black-optical-paint.html

This stuff is meant to be good too- Rosco supply film and broadcast with super saturated paints- for green screen studios etc. More economical than black 3.0 too. Might have to experiment...

https://shop.flints.co.uk/Products/ALL/ROS16003

1 minute ago, Stu said:

Hmmm, you need to get yourself all these....

Telementor

Alkor

TS 72mm Doublet

Televue Genesis

FC100DC

Vixen FL102S

TAL 100r

Vixen 102mm f10 PST

Heritage 130p

Orion Optics 8” f8

Mewlon 210

I’m bailing 😂

🤔 its good to know there’s an explanation but that maths- no not really 😂 So the Alcor produces similar disks? I don’t remember but it might

Oh I just realised I seem to be exactly copying you Stu 😳 I too have an 8”f8 (well ok an 8.75 f7.4 but if I stop it down it’s the same), now a telementor, an Alcor (well I had that before you I think) and am about to build up a 100rs! Not consciously doing it I promise 😂 (what were your other scopes Stu? 😉)

2 hours ago, Stu said:

Iso the other day I stood it upright, loosened the retaining ring on the objective, and tapped the tube all round before tightening up again. I’m pleased to say that it appears to have fixed the problem! 

Yes I find whacking things usually does the job too Stu! 😂

I didn’t get to bed till 4 this morning- such perfect conditions and what an incredible huge moon! Out with the telementor- a mixture of joy and more frustration with the mount and inaccuracy of setting circle goto- I will master it eventually! First view this season of old favourite Albireo, failed to split Pi Aquila, failed to split Zeta Herc, couldn’t find ring or dumbbell- probably jiust the moon drowning them out but did split a few other beautiful doubles, saw a very bright bolide (could I have actually heard it?!), and had packed up when I noticed a new bright star on the SE horizon- first and rather perfect view of mini Jupiter and Saturn- wonderful 😊

I will dig out the Alcor Stu- hope it still works as haven’t used it for decades 😳 I don’t remember Jupiter looking anything like as sharp as it did last night in the mentor though, but it had perfect pin point stars.

One thing has me puzzled though and this may be a question of refractors in general but I’ve noticed stars appear as tiny disks in the mentor- perfect round as you say “bullet holes” which seem to vary in diameter according to brightness. I never noticed this with my big dob which shows pinpricks just with varying fiery noise depending on brightness. It’s quite attractive these disks but it’s not real is it- is it a phenomenon of refractors? Any idea what causes it? Stars are so far away they should appear as infinitesimally small point sources shouldn’t they? 🤔 I think these refractors cheat! Pretty though 😉

Does flocking tend to hold moisture? 

I think you could drive the worm direct with a motor like this: https://www.omc-stepperonline.com/nema-23-stepper-motor-8mm-single-shaft-for-face-mask-machine-and-respiratory-ventilator.html

or chose one half that torque and gear it 2:1 with belt but that would halve the slew speed. It requires 2.8 amps for full torque though so better check the drive can handle that. 

What will you be powering it with?

So what was your question again 🤪

Are you going to buy a system from AWR or looking to replicate it?

And I think I made a mistake about the max rpm- the trinamic boards can drive the motor up to about 300rpm and AWR site seems to spec for 120rpm so slower slew  rates. Sorry for the confusion

Sorry Dave, I completely misread your original post and didn’t click the link to AWR motors. I thought you were talking about your original motors 🤦‍♂️. 

Hi Dave, this looks like a gear head but it needs the extra gearing because it’s a higher speed lower torque motor. In your case looking at the numbers I don’t think you need any extra gearing than the worm at all.

If you’re going to use microstepping drives then you probably don’t need to worry about steps- you can work out what one micro step will be in the output once you’ve decided on motors and gearing

suppose you want 10 deg  per second slewing, that would be 1.66 rpm. The worm ratio of 360:1 would mean you’d need to turn the worm at 600rpm (handy) with a torque of 1-2 Nm. So you could buy stepper motors with that sort of torque- Nema  23 perhaps and drive the worm 1:1. With 256 microsteps that would give you 256 steps per degree of output motion. Sounds ok to me but I don’t know. You couldn’t go any faster than that unless you really over rated the motor torque to allow for torque fall off or geared up a more powerful motor but at loss of resolution. You could go slower than that and get higher resolution- 5deg per second would double the resolution to 1/512 degree by adding the 2:1 belt drive. You may not want to run the motor at full speed for noise reasons.

Hi Dave, yes you have 360:1 worm ratio and if you use the belt multiply that by the 2 or 3:1.  It looks like there’s a planetary or spur gear stage on the motor itself? That will have a ratio too which you multiply also. That will give you the final ratio which will divide the input motor speed to give you an output speed (speed the scope moves) and multiplies the motor torque minus losses (friction in the gears).  The trouble with choosing the max slew speed is you need to base it on the stepper max speed of 600rpm but you need to keep enough gear ratio to not have issues seeing the steps at the eyepiece. The higher the final gear ratio the slower the max slew rate but the smaller the step and smaller the motor. If you want faster slew rate you need lower final gear ratio, stronger motors and need to think about output step size. Not sure what would be an acceptable output step size though. Are there or could you add clutches so you could slew  the scope by hand then let the motors take over?

For a starting point 8lb inch is about 0.9 Nm so if you aimed for 1-2Nm output torque you should be good. For gearing bear in mind steppers have limited max speed of about 600rpm before their torque falls right off. So you need to work back from the final slew speed you’d like or if you only want sidereal motion multiplied by the worm ratio and then chose an intermediate gear ratio to multiply to give 600rpm on the input. Then use that intermediate  gear  ratio to divide the 1-2Nm to get your motor torque and maybe add a bit for losses. You could use micro stepping drives to get smoother quieter motion but they use power to hold between step position. But full step you'd need a high enough gear ratio to not see the steps at the ep which would limit your max slew speed . I think I got that about right but will reread just in case

That’s why I was so surprised- the sky was awash with thin high altitude cloud cover! I had no hope finding M13 with those conditions though and didn’t even try for the ring neb

I should dig my Alcor out of storage! Nice report Stu. I spent a very enjoyable evening getting to grips with the setting circles on the telementor mount- have just about got them cracked now 🤞 Izar and Castor were lovely and I was pleasantly surprised at easily splitting the double double despite it still being quite small in the fov and the stars pinpricks! I didn’t expect to see Polaris’s partner but there it was- a tiny sharp spec with the 16mm and even fainter with the 6- but definitely there! I might have seen Y4 Atlas but hard to be sure and probably not- nothing that looked like a comet anyway and I might have seen Herschel’s Garnet star but if I did it wasn’t very red! Really fun night though 😉

Well @bomberbaz, after a really enjoyable 2 1/2hrs last night I can thoroughly recommend persevering with this technique! So much better than the previous session. Ok the weather played nice- mild and only light breeze, and fixing the slo-mos meant the mount was at least functional! But there’s something enormously satisfying about dialling in those numbers then finding your object bang there in the middle (ish) of the eyepiece! Last night especially so as I could only see the brightest stars through the light high altitude clouds so little chance of finding things by eye! Yes it’s time consuming compared to a computerised goto or swinging a dob round to a well known target but as it becomes more familiar I’m finding it very rewarding indeed! 

I figured out how to use SkySafari’s 12hr E and W hour angles on my 24hr scale and it’s actually pretty straight forward- any E value requires a meridian flip and then I just have to count the hours backwards from the 12o’clock marking. Sounds a bit complicated but it became easy with use. This is great as I’m not fond of the stellarium user interface and last night it seemed to be giving wrong values anyway! 

I had to tweak my hour circle and polar angle a little again but have arrived at being able to put any target E or W of the meridian within the 25mm ep fov- this is really great. One thing I noticed that i now keep an eye on is with the tripod on grass or other non firm surface like decking, swinging the scope around or on decking just standing near it will affect its level as seen in the bubble and if that’s off then everything is off! I had to re-level several times but that’s quite easy to do.

In praise of the telementor T-mount, it kinda looks like a piece of surveying equipment and it really feels like a precision instrument- it was a joy to use in this way now it’s fully functional.

Bit pointless adding to this as you’ve had excellent advice and made your choice but another option might have been the Petzl e+lite. I was using mine just last night and it’s got some really nice features. A lever to turn it on with off positions at either end of its motion means you can have it always go to the red LED position first. It’s tiny and very light so you barely know you’re wearing it. Downside is it runs off CR2032 coin cells. I don’t suppose they’ll last very long but on low power red LED probably long enough- I’ve not used mine long enough to find out. So far it’s been excellent and the red light is enough to see the setting circles on my mount but dim enough to barely notice it’s on otherwise 👍

10 minutes ago, AdeKing said:

What about investing in some cheap binoviewers?

With the tube being that much too short, you'd be near to achieving focus natively with BVs without needing to throw a Barlow into the mix.

Just a thought, although you'd need to do a bit of measuring to be sure.

Pretty sure that the original Maxbrights with a T2 prism diagonal have a light path length of 148mm.

Worth investigating maybe?

But then I’d have to buy loads more eps Ade 🤷‍♂️ 😂

45 minutes ago, DaveL59 said:

 just measured my 100RS, between the holes for the objective and focuser its 72.5CM if that helps at all. Was the tube modified in the past then?

That’s the same length as mine Dave thanks. But the og Tal focuser has a really long tube- this one is 185mm. That leaves me about 8cm short- a bit more to be safe with all my eps (the Siberia 50mm erfle focuses 15mm inside the barrel step) 

Dave F15rules thanks- I’m toying with the idea of just making a longer tube- maybe a nice polished aluminium one or I’ve been looking at phenolic rocket tubes!

8 minutes ago, DaveL59 said:

Not a TAL100 OTA is that Mark? does have a very familiar look to it esp with those rings  

Well spotted Dave. Trouble is it’s an RS with short tube and it lost its og focuser so I’m going to have to figure out a way to extend it I think...or new tube 🤔

New focuser

Almost a new telescope!

Hi Joc, Saturn is a gas giant like Jupiter! I wonder if it’s just because it’s smaller in the ep so the illusion is it’s sharper/more contrasty 🤷‍♂️

It’s weird though how Saturn usually appears sharper to me yet it’s twice as far away!