Stub Mandrel

On 24/06/2020 at 12:44, TerryMcK said:

Most of us have 50mm guide scopes and getting them into focus can be hit and miss. Most of the time it is easy to get the stars as small as possible but it is only guess work. So I ordered one of these Bahtinov Masks from astrograph for £30+ postage and it came earlier today. It is one of the only ones for 50mm lenses I have found so far. It is made from metal and is quite heavy so I don't think it is aluminium. I could have made one but the Bahtinov generator produces such fine lines that it is impossible to cut from black card (I know as I've tried!)

This one has a M52 thread but they do it in M49 too. To mount on the guide scope I will just use painters tape.

It will have double duty as it will also fit my prime 50mm f1/8 Canon lens for ultrawide field work. I will use an adaptor to fit it to the Canon.

 

 

 

I use a 3D printed one.

Managed 34 5-minute Ha subs last night, 150PL, ASI 1600MM, and got more than I expected, considering the combination of murk and light pollution. I think the corners are vignetted, despite using a flat.

Now I need OIII and SII.

<edit> revised with a version to address vignetting.

A few nights ago Antares was such a brilliant red I made the ages-old mistake of thinking it was Mars...

1 hour ago, Blazar said:

Never bothered with an ADC (but I did buy one), and I have a 174mm...I guess shooting with a colour whilst they are low is ideal and the ADC is beneficial... Jupiter is around -20 degrees below the celestial equator even at the meridian. Probably why I have not been out for two years or so! 

Makes a big difference, I would have put planetary imaging aside if I hadn't got it. I was convinced my setup was broken in some way, but it was just atmospheric dispersion.

21 hours ago, Chriske said:

Urania...😉

I'm afraid  I had to use Google Translate as my grasp of Flemish is tenuous. You may be horrified to discover that Google treats it as Dutch...

Actually, it does a very good job (which isn't surprising given the shared roots).

I am impressed by the website and will definitely head for Urania if I visit Belgium again.

2 hours ago, Ricochet said:

Triangular stars are usually caused by the primary mirror clips being too tight and pinching the mirror.

Yes, but it's glued at the neutral points, its also 3/4" x 6" mirror so a lot more rigid than say a 3/4 x 10"

Had to go back and see what I could find. This is the RGB image I ended up with.

Compare with RGB image a couple of weeks later:

Perhaps a lot of the difference is the processing?

Just an observation, it took months of work to sort the secondhand 3m dome on our club observatory.  So many things to put right...

Did a test last nigh. At 11:45 it read 19.22 and at 1:15 it read 19.40, aimed at the darkest patch of sky (CO suggests I am 19.66, but that would be during astro dark).

Without access to the exact formula for calculating Lux, I can't be sure of the resolution but after changing my code to take four readings and average them the final SQM readings seem to have a resolution of about 0.02 right down to well past 22.

19 hours ago, JamesF said:

I had a bit of a "Swiss Toni" moment there

James

You haven't got a clue what you're doing and are so stressed that when it's all over you aren't sure if it was worth the effort ...

On 18/06/2020 at 14:14, inFINNity Deck said:

Would love to hear how that curved spider performs.

Nicolàs

 

It doesn't make spikes, a star test suggests that it makes out of focus stars a bit triangular but I need to do a proper test on a bright star now I've flocked it as it may be caused by reflections off the white tube.

On 17/06/2020 at 13:47, The Admiral said:

*Edit. Below I've plotted the the read noise against ISO, with the ISO scale linear rather than the usual log scale, and it shows more clearly where the read noise levels out.

 

@Heskyyyyy the short answer (borne out by @The Admiral's graph above) is that most folks use ISO800 for the older Canons.

4 hours ago, Chriske said:

I know Neal, but doing that, I lose my hobby.
Now I'm having fun, making these things at my own pace.
You're not the first pointing that out to me  btw...😉
Thanks for the kind words btw

I understand, having seen a hobby become (in part) my job, I know what happens!

11 hours ago, Chriske said:

View from another angle while working on HST today.
SaturnV in the right corner is the one I made before, it is 2m high

 

Thanks for the link.

Hubble makes the Saturn V look tiny! Would be great to visit the museum one day.

(You do realise there are places that would pay you to make exhibition models of that quality...)

6 hours ago, Chriske said:

One of the last things that will be mounted are these three little guys.
They are needed as last balance control of HST.
Two mission specialist (Michel/Chris) and the third (Marc) is the guy taking care of the finances to build this HST

 

Excellent! Is that a freely available STL file?

What would be most effcient would be a hot end fed with powdered/shredded PLA that fed a metered flow of molten plastic directly to a hotend.

You would probably want a fixed hotend so a table moving in X and Y (and maybe Z) but that woudln't be difficult to arrange.

I suspect a dual feed so an archimedes screw to feed the pellets into the melter, and I wonder if some sort of peristaltic pump could work at a high enough temperature to give precisely metered delivery ?

48 minutes ago, Gina said:

Oh sorry Dave - that post was off-topic.

I started this thread, and as one of the most discursive people on the planet, I can't complain if it goes awry!

2 hours ago, stash_old said:

No matter what - the same applies to all the kit you/we use in Astro world. 

Sorry Stub Mandrel about high jacking the thread. 

I will not  post anymore on this thread about environment but if Julian wants to start up a new thread on the whole subject fine.

2 hours ago, Dr_Ju_ju said:

Absolutely, but no more 🙇‍♂️ .... sorry Stub

LOL!

I'm a chartered environmentalist.

My main guilt is the large amount of failed 3D print prototypes I have building up; quite keen to look at a way of turning them back into filament.

But... the environmental cost of a kg of PLA every month and the relatively modest amount of power used by the printer? Compare to any hobby or pastime that requires you to drive.

As for my hobbies in general they don't involve large amounts of material and put me in good position to keep, repurpose, repair, reuse, recycle...

22 hours ago, JamesF said:

Other than sorting out life under our new viral master, making up the bracket has probably been the major reason for the pause in constructing my Robert Brown auto focuser.  I need to make up a bracket to fit a Steeltrak.  I really must get on with it.  How much cost/harassment is it to set up a small anodising rig, Neil?

James

More harrassment than cost, you need to safely access and store sulphuric acid luckily a dilution just below the level where you need a licence for it is ideal (about 12%). Also sodium hydroxide, for stripping and degreasing. So a sealable plastic box as a tank for the acid, that lives in a bowl with washing soda in it  to neutralise any drips. Lots of PPE - goggles, gloves, plus croc clips, wires...

I bought proper dies (which will last a long time before being exhausted) and sealer, as these make the colours more consistent.

I made a cathode by melting down lead pipe and pouring it into  a (very dry) wooden mould.

I have a long titanium rod for mounting workpeices, it needs to be polished to a clean finish with wet and dry to ensure good electrical contact.

Other equipment is a 4A transformer from an old battery charger and an old style moving iron 5A meter. The meter swings full scale then rapidly drops, rather than set the current I keep going until it starts to drop.

I've only had one chance to use it so far! It was quite nice but the tube wasn't flocked and the sky was a bit bright so I only saw a few brighter objects.

I want it to be my main visual scope, on the EQ3, while I'm imaging.

For the amount I need, it would be cheaper to use an existing offcut, or I can copy ZWO and just screw two bits together.

But I'll probably 3D print it for now and make a pretty one when my anodising is set up again.

I might make another one, for my 150PL, if I do that will need some sort of belt drive because it's the focuser you can't the the knobs off.

It looks like if you take the rubber grip off the knobs, they are like a big pulley.

I'll need to do my own design, because it's a self-made focuser.

On 13/06/2020 at 22:55, fozzybear said:

Neil,

This has me thinking for my SW 72ED and find a bracket to fit the motor to or find one on thingiverse. I've got Nano's and some of those 5v motors with boards somewhere (stolen from my son) 🙊 he won't miss them. now to look at @tekkydave Arduino code

would you use a direct coupling or belt drive?

Cheers

Andy

I'm going to use direct coupling like the ZWO units.

Yes I might end up with a 3D printed bracket, rather than mill away 95% of a lump of alloy!

My 3D printed (mostly) 6" f6 Newt.