markse68

Good question! I tried everything culminating in through bore latching toggle which was the only thing that came up with this 🤷‍♂️

https://www.kipp.com/gb/en/Products/Operating-parts-standard-elements/Spring-plungers-indexing-plungers-ball-lock-pins/K0776-Socket-pins-with-folding-latch.html

53 minutes ago, Wiu-Wiu said:

Here's a sketch by a friend in a 10" dob:

 

You need to beware that the pup often hides right next to a spike. Maybe that's what's throwing you off? 

Hi Wiu -Wiu, yes I had heard that and as a consequence rotated my scope tube several times during the evening in an attempt to avoid it- I don’t think it was hiding in a spike but maybe- maybe I managed to rotate it exactly 90 degrees each time 🤔

3 hours ago, John said:

I did check the field stars with the 130mm refractor and they matched those that are in my sketch although N & S were reversed in the refractor of course.

As Craig says, you just have to keep trying and one night things will come together

This is strange- I guess you’re seeing these field stars

but I’m seeing maybe some of these 🤷‍♂️

Anyway- yes I’ll keep on trying 😊

4 hours ago, CraigT82 said:

I also had a quick go last night with the Fullerscope and couldnt manage the split, though I have managed it previously with this scope though.

Sirius is pretty low down and with all the people with their heating on I think the local seeing was pretty poor.  Just got to keep trying!

In my bortle 8 skies my limit with the fullerscope is about mag 11.5 IIRC. 

Thanks for the encouragement Craig- good to know that it should be possible with my scope and my sky.

How did you go about establishing the magnitude cutoff for your scope? Just look for known magnitude stars incrementing  till you can’t see them?

Had another go tonight. What with the record high pressure we’re in and clear skies forecast I reckoned it would be a good session so I had a “take your scope to work“ day- leaving it in the car all day to make sure it was nice and cool. Paid off in a way- scope was firing on all cylinders straight out the car with nice tight stars and almost perfect star testing 👌. As I’d hoped seeing was really excellent tonight- probably the best I’ve ever had. And no wind 😳 which really helped a lot. I saw e and f stars in the trapezium quite clearly- first time for f! I was able to split Rigel easily with a 20mm ep- just 80x mag! Sirius was a nice tight image too- by 10pm it was reasonably high and not the usual disco ball you see at lower elevation. I must have stared at it for several hours. I tried all my best eps from the 20mm through my medium power orthos to my Nagler 4.8. Even tried barlowing the orthos to get 3mm for max 500x. Still no joy 😞. I reckon if I was going to see it tonight was the night. It must be too faint for an 8” scope under Bortle 9 skies I guess. Still it was a really great night and an enjoyable if frustrating challenge. 

Weird how we see different field stars @John! With my Nagler which should give a similar magnification and fov I think, the dominant field stars formed a W rotated to the nw of Sirius in the ep view 🤷‍♂️

23 hours ago, John said:

This is how it appears with my 12 inch dobsonian if that is any help. The Pup star trails Sirius as it drifts across the undriven field of view. The position angle has changed just a little since this sketch was made a year ago (to the day !):

 

Hi John, had another fruitless look at Sirius last night but I'm a bit confused as I’m not seeing the surrounding stars like in your image. Is this a magnitude thing? I looked in sky safari and can’t see the line of stars either.  I guesstimated your fov and played around with magnitude settings - was there something else in your fov that wasn’t a star/s? 🤔

49 minutes ago, John said:

This is how it appears with my 12 inch dobsonian if that is any help.

Great thanks John- is that it there?

15 minutes ago, Stu said:

I've not been able to find a good reference to the angular position for Rigel, although the separation is similar to Sirius as has been said.

Thanks for looking Stu- guess what we need is for someone to actually see it tonight and give the rest of us the info 😉

34 minutes ago, Captain Magenta said:

but it was an 8" newt on an EQ mount,

Hi Magnus, yes indeed I’m never really sure what’s up down east or west looking through mine (also 8” newt) I’m going to check on stellarium when I get to a pc next- does that give accurate positions of orbiting double stars though 🤔 So my thinking is use Rigel as a reference for both separation and an angular offset position for where to concentrate efforts and to turn scope tube to ensure diffraction spikes (very strong on Sirius!) are not obstructing where it should be. Will have another crack tonight at Flamsteed meet-up where hopefully there’ll be some big fracs too- I’m not giving up 😉

Any idea how it’s position should be  relative to position of Rigel b Stu? For some reason SkySafari doesn’t show Rigel b 🤷‍♂️ Last night I was out for about 3hrs under clear skies and spent a lot of that time just staring at Sirius wishing the pup into existence but of course it stayed in hiding. Rigel b was at 12 o’clock and obvious. Relatively where should the Pup be? It wasn’t the best seeing though- I couldn’t see trap E star which I’ve seen before a few times.

8 hours ago, Stu said:

I had a somewhat futile look at Sirius, pushing the power right up to over x400 with no luck, too much flaring going on unfortunately. I've still yet to see the Pup!

Why’s it called a mewlon  Stu? Is it a type or just a model name? Nice looking scope either way

I'm starting to think the pup is just too faint for our London skies but I’d love to hear that’s not the case. It’s about the same separation as Rigel's double isn’t it? At ~300x I’m getting plenty of separation on Rigel to clear Sirius’s flare but no joy seeing the pup

7 hours ago, johninderby said:

Never bother with a primitive ND filter. Find the Baader neodynium gives me better views. 

Why is an nd primitive John? Neutral density should affect all wavelengths evenly so it should just dim the view without adding colour shouldn’t it? Or are they really not nd?

Can you elaborate on “better”? I think people use the classical large journal dob bearings with goto and push-to too? I’m really interested in the comparative “feel” of these- the balance of friction/stiction and how useful the adjustability is?

Mark

Just wondering do such fine threads actually print 3D? 

The background of the current image is a bit lighter than the older image so it’s even dimmer?

Yes there’s something to be said for the beautiful simplicity of the classic large trunnion + Teflon and Formica solution though I think there’s a bit of an art (or rather science) to getting it right- trunnion diameter/pad spacing/Formica surface texture to match OTA weight and inertia that could be tricky for a diyer to get right without a lot of trial and error. Especially given differences in preference to the balance of stiction/friction. Some sort of adjustment mechanism seems ideal but it would need to not only adjust the kinetic friction but somehow to skew the relationship to stiction too 🤔

Is that what’s causing this pop up requesting acceptance but no way to accept? 

Thanks John, using that knowledge I found a few results on CN referring to them but no detailed discussion about them- just that some like them whist others don’t 🤔😂 They certainly look a neat solution and well made 👍 I wonder if they just have too little stiction- the stiction is too close to the friction? I guess a little stiction is useful for giving the right amount of lock when changing eps or in the wind. Yet most of the discussion on alt bearing design on CN are about reducing stiction to make it closer to the friction to prevent jerky motion- something I’d obviously like to minimise in my new dob base design. Maybe there’s just no perfect solution that will please all users

I just spotted this on Teleskop-express website and just wondered if anyone has experience with such a device- do they work well? Wondering if the friction is smooth or if it has stiction and if they stay set or work loose?

https://www.teleskop-express.de/shop/product_info.php?products_id=6767#ebericht

Thanks,

Mark

PS happy new year

I got one hobby related pressie- can thank  @Second Time Around for this 😉 Was hoping for white but never mind 🤦‍♂️ (I’m so ungrateful 😬)

Bit late but merry Christmas fellow stargazers/pic takers 🥂

Assuming you have a Newtonian scope (?) worth checking your scope isn’t way off collimation as that will change alignment of the finder too

The cupped standoffs were meant to make attachment in the dark a bit easier- self-aligning, but they didn’t work out. They directly coupled the fan vibration to the tube in a bad way. So I’m back to plain flat standoffs but larger diameter. This seems to work great- can barely feel any vibration in the tube and can’t see any difference even at high mag with fan on or off. I made a mistake measuring the id of the tube with a tape measure and ended up making the Perspex disk about 3mm smaller but this has turned out to be a blessing as it can be mounted without direct contact with the walls and the Velcro does seem to be working well decoupling the fans.

And the fans do really help- star testing I’m getting pretty stable diffraction rings in the Airy disk. I do seem to have some spherical aberration though- the rings are clear on one side of focus but a blur concentrated in the outer ring on the other with barely discernible rings. Could be the glass still not in perfect equilibrium  or the cell not supporting the mirror correctly or an imperfectly figured mirror I guess. But the image is much clearer than I’ve had before so I’m not going to fuss too much about it.

The new secondary was a very worthwhile investment too- no sign of the astigmatism I was getting star testing with the old mirror. Feels like all the improvements really are improvements and I’m getting the best from the primary now 😊

15 hours ago, johninderby said:

Many would be surprised to learn that the Betamax broadcast recording camera system Betacam was in production until 2018 and is still used by some smaller broadcasters.

I used to get cast-off betacam tapes from work thinking they’d be high quality for my old Betamax machine- wrecked the head with their fancy “metal” tape 🤦‍♂️

Thanks Stu- I figured that even though £20 is more than I’ve ever spent on an app before, I couldn’t get much anywhere near as useful in this hobby for that price (a £20 ep wouldn’t be up to much 😉) so I went for Pro! 😊

Will have to wait a bit before I can try it though 😳😂 

On a a separate note, do you know if there’s a way to better align the AR view? In the basic version it never seems to quite align with reality 🤔 On another app called SkyView lite there’s a view calibration widget that you can manually slide the view to align it but I can’t find anything like that in SkySafari 

I saw this too Stu. Do you know roughly what it gives over the free version and is it worth it? If I wanted to add push-to with a dsc to my dob using something like the Nexus II would I need the pro version?