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  #1  
Old 19-02-2018, 07:58 PM
derku
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derku's skywatcher 150/750 newb(newt) blog

Hi all,

As someone who was always interested in celestial images, it led to a hobby of amateur visual astronomy. It began by testing waters with a Celestron 70 refractor on an eq mount more tailored for perhaps kids. Poking around in the sky was enough to entice the interest further which I hope will develop into a more in-depth and long standing hobby.

After a bit of time browsing around on ebay and gumtree for a more powerful telescope; albeit used scope as to respect my finances, the journey started when I bought a skywatcher 150/750mm with EQ3 mount from a nice young chap whom was downsizing his gear.

http://www.iceinspace.com.au/forum/a...1&d=1519031695



Took it out for a spin and took a quick snap with a samsung galaxy s7 of our moon. I noticed some artifacts which Im guessing is to do with the phone's digtial compression. I also noticed some chromatic aberration and a lack of contrast. This was taken in Homebush Sydney on top of an apartment next to several light posts.
http://www.iceinspace.com.au/forum/a...1&d=1519032156



Anyhow, it was proof enough that the telescope would be suitable for my endeavours. The plan, or goals perhaps, is to see Saturn's rings visually and take a few photos of the Orion Nebula or Andromeda galaxy.... yeah, pretty typical I guess.

Being a used telescope, here it sits now and I have some plans for it but firstly taking it apart for a good clean and service.
http://www.iceinspace.com.au/forum/a...1&d=1519032156
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Last edited by derku; 19-02-2018 at 08:58 PM.
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  #2  
Old 19-02-2018, 08:16 PM
derku
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baffling

The first part of disassembly was just to clean the optics because peering down the tube saw specks of dust but until it was apart and a close up look, revealed this grotty mirror I'll be giving it a good clean with basic gentle hand wash and some demineralised water that I'll pick up from bunnings...
http://www.iceinspace.com.au/forum/a...1&d=1519034821



Because I reside in Sydney CBD area, light pollution is high and it led me to research on ways to reduce unwanted light entering my scope. A bit of research led to the idea of baffling and flocking inside the tube.

The geometry was solely taken from this online generator "Newt for the web"
https://stellafane.org/tm/newt-web/newt-web.html



The profiles were extrapolated from the online calculator and laser cut out of 3mm mdf wood with a notch to clear the seam joint of the optical tube. The wood was given a spray of matt black by none of than the good old Australian export spray paint.
http://www.iceinspace.com.au/forum/a...7&d=1519034821


After spray painting
http://www.iceinspace.com.au/forum/a...8&d=1519034821



Photo of the tube taken before baffling
http://www.iceinspace.com.au/forum/a...9&d=1519034821



Aligning each baffle according to spec with three marks inside to ensure each ring sits true and parallel(perpendicular?) to the length of the tube. They were cut so it was a nice snug fit although they will still be glued in later. What one thought would take 15minutes to align 10 or so baffles... took about 2 hours
http://www.iceinspace.com.au/forum/a...0&d=1519034821



More updates to come, thanks for viewing thus far!
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Last edited by derku; 19-02-2018 at 08:56 PM.
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  #3  
Old 19-02-2018, 08:50 PM
derku
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flocking

So despite the inside of the tube being painted matte black, those properties were still far from the best when absorbing light, or more-so minimising internal reflections from unwanted light sources. I read up that adding flock inside the tube, would reduce oblique reflections and increase contrast. At this stage I thought it would be a great idea considering I would be using the telescope in an urban environment. Regrettably, I say this with emphasis... or perhaps a poor decision in hindsight, was to flock it traditionally using glue and flocking powder... this was before I realised there were adhesive strips...

Oh well, I had already invested in flocking powder and some PVA glue... so I was already committed to that. Painting a few segments of the baffles, whereby gluing them in at the same time, involved careful brushwork to ensure an even layer of glue ... but then a sprinkle here and sprinkle there resulted in my first flocked section of the tube!

You can still see the glue drying in this pic:
http://www.iceinspace.com.au/forum/a...3&d=1519037060



Closer up shot showing that the coverage was pretty good actually
http://www.iceinspace.com.au/forum/a...4&d=1519037060



Took a photo at the other end to see if the flock(and probably baffles) actually traps light, and this photo confirms that it does something... but not sure how to quantify
http://www.iceinspace.com.au/forum/a...5&d=1519037060



After the whole tube was flocked, you can see the baffles are all aligned and consistent meaning the calculator... or I should say the way I followed and didnt stuff up the calculators dimensions, produced the correct geometry as to not obscure the primary mirror in any way, yay! well, photo doesnt show the mirror but ill post it up when its all dry.
http://www.iceinspace.com.au/forum/a...6&d=1519037060
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  #4  
Old 19-02-2018, 09:11 PM
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Steffen
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Cool project! Where did you get the baffles laser-cut?
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  #5  
Old 19-02-2018, 09:16 PM
derku
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Quote:
Originally Posted by Steffen View Post
Cool project! Where did you get the baffles laser-cut?
I did it myself with a machine at work. Although, any architecture craft shop could do it. Just supply a .dxf drawing and it'd be around $30 a sheet for 800x500mm and if you're strategic about placement, you could get a lot from one job. i.e. smaller objects inside the circles of the baffle rings can host a wealth of other parts. Sorry I do not have a specific vendor at hand to recommend...
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  #6  
Old 19-02-2018, 10:11 PM
SkyWatch (Dean)
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Congrats on the new scope derku! Great job on the baffles too. You will probably get a longer lasting job with your flocking powder and glue that you would have from tape anyway!

BTW, the CA you can see in the moon image wouldn't be from the scope: a newtonian (ie: mirror) doesn't produce CA; so it must be from the camera.

I hope you have many happy hours viewing with this!

All the best,

Dean
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  #7  
Old 21-02-2018, 06:40 PM
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Great job so far , well done ! .
I will be waiting for part 2 .

Brian.
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  #8  
Old 22-02-2018, 12:00 PM
derku
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Thank you Dean and Brian for the praise, I'm honestly just doing things under my nose as I go along...




I stumbled across this youtube channel "astronomyshed" by a gentleman from the UK who modified his focuser by increasing the contact patch by sanding/filing it with a sharpening stone.

https://www.youtube.com/watch?v=ofOSAMlqZWw

He depicts the issue that the shaft only contacts the edge of the focus tube's slot and thus a poor surface area to exert the friction upon. This image was from his youtube video but I had the exact same marks embedded on my focuser prior to his suggested mod.
http://www.iceinspace.com.au/forum/a...1&d=1519263994



So that sent me on a quest to follow his guide by dismantling the whole focuser assembly and I was glad I did. There was a cake of dust between the crayford shaft and the teflon sleeve which Im guessing caused some of the slipping problems I initially had. After a good clean:
http://www.iceinspace.com.au/forum/a...1&d=1519263994



Close up of the new contact patch shows that the shaft now glides along a much wider surface area. It feels significantly more secure with less tension on the grub screw. It can also comfortably hold a 1.2kg camera without slipping down, without the locking screw! The smoothness is about the same. Also, you can see flock tuffs stuck on there randomly... what a nightmare it is to clean those off as the static just attracts it back (everywhere!).
http://www.iceinspace.com.au/forum/a...1&d=1519263994



Not sure why skywatcher decided to use this glittery silver for the focuser tube apart from external aesthetics... but one would guess it'd be no good when it protrudes inside the OTA. Time to flock that as well but care must be taken to mask out where the bearing guides run to ensure smooth operation.
http://www.iceinspace.com.au/forum/a...1&d=1519263994



Focuser flocked and reassembled... not sure if itd make any difference at all but its done
http://www.iceinspace.com.au/forum/a...1&d=1519263994
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  #9  
Old 22-02-2018, 02:32 PM
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I ca t offer proof the following works but I think it helps exclude street lights at least.
I made what I would call baffled dew tubes for most of my scopes (not the 12 inch).
Its a tube about 2.5 feet with baffles painted black and sprinkled with saw dust and painted over.
If you look at the Hubble Space Telescope you will see they do this...they mention something about a stray light thing.
I have not done any tests to show there is a difference but I think the contrast is better...
Alex
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  #10  
Old 22-02-2018, 08:32 PM
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Good pick up on the ' Glittery ' draw tube , it really cant help when its sticking in the light path bit silly really but hey ,,,, it looks pretty ,,, .

I am sure what you did will be more of a help as every little bit helps .

Keep up the good work .

And yes Alex's suggestion really works , I have a Celestron one on my C9.25 and there is a marked difference in contrast between using it and not , especially when there are a few lights about .

Brian.
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  #11  
Old 23-02-2018, 07:37 AM
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Hi Brian
I thought I was alone on the idea so I am happy to see that I am not the inly one who thinks it is a good idea.
Alex
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  #12  
Old 23-02-2018, 09:29 AM
SkyWatch (Dean)
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Definitely a useful idea Alex. Anything to block stray light really helps. I doubt that the hubble telescope uses painted sawdust though.

I have been known to observe with a full hood (a bit like Obi wan!) in the backyard to block more light from hitting my eyes. Works really well, you just have to have a handy light sabre to beat off the laughing wife...

Looks like it is all coming together well derku: and good pick up on the increased contact area for the focuser. I don't think I would flock the focuser (just more bits to float around!), but spraying it matt black wouldn't hurt.

All the best with the mods: in my experience they never end; there is always some improvement to be tried.

- Dean
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  #13  
Old 23-02-2018, 09:51 AM
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When into visual I had a cover thing but most important was an eye patch. ... if my eye was not at the ep it was covered...sounds strange but guess what it works.
In fact I need to make a new one.
Alex
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  #14  
Old 23-02-2018, 12:52 PM
derku
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@Dean; thank you for the encouragement... I need to put more hours into actually using it rather than just working on it!


@Brian @Alex; now you have sent me onto another quest on developing a dew shield...! Actually I'm still reading up on how effective they actually are, if at all and if its necessary around east coast urban environments... but I do appreciate the idea that a tube extension can block out more foreign light such as street lights.



I found a nice website "darksitefinder.com" to indicate optimum areas of (minimum) light pollution. I havnt updated my profile yet but I basically reside in the red to orange band I've never pointed telescope in any darker area actually and I guess asking for any 'dark' sites within the city is another thread topic all together.
http://www.iceinspace.com.au/forum/a...1&d=1519353008



Minor update is that Ive washed the mirrors using regular hand wash that foams up along with demineralised water from good old bunnings. The demineralised water was suggested as is doesnt streak when drying but Im not sure about that. Despite warnings about not touching any of the mirror reflective surfaces, I found I had no choice but to rub it slightly with my fingers (whilst washing with soap) to get some of the stubborn dust/contaminants off the primary mirror. It also took a few goes because the stupid thumb(s) kept slipping back of the surface (no thumbs down emoji which would be more suiting).
http://www.iceinspace.com.au/forum/a...1&d=1519353375



Pretty much ready for reassembly as the flock has dried. A few passes of compressed air loosens the un-bonded flock filaments and a gentle wipe with a damp micro fibre cloth takes care of any other loosely held flock.
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  #15  
Old 23-02-2018, 08:18 PM
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Looking good.
I thought of the dew tube light control because I was at a dark site astronomy each night every night up all night slept all day for years I lived that way...I only went shopping if it was cloudy etc...obsessive to the power of ten.

I could read newspaper head lines under just star light.
We see stars as little dots but their light spills all over.
It occured to me just the glare from Sirius must be a problem ...its not just a dot ...seeing it that way I became very conscious that ots light was greater than just a dot...it fell into the tube all over ...thats a lot of light.
Even if you do a zaw dust model it should help but I believe baffles are necessary...light can still bounce off saw dust but a baffle stops it and sends it back up the tube...draw something showing light paths from one star and you realise it goes everywhere.
Alex
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Old 10-03-2018, 04:16 PM
derku
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Pretty crap weather lately so not many opportunities to test anything out.

Just some photos of the flocking job and assembled telescope.
http://www.iceinspace.com.au/forum/a...1&d=1520662273


Pretty dark in there now.
http://www.iceinspace.com.au/forum/a...1&d=1520662273


Got some ideas for a fan and then its onto servicing the mount. Ordered some superlube for the worm gears, so fun times ahead... Still doing a bit more reading up on dew shields but I do intend on making an extension to block out light pollution scatter if nothing else.
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Old 10-03-2018, 10:36 PM
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WOAW ! that flocking looks impressive , I bet it really makes a difference at the eyepiece compared to standard ,, , well done .

Personally I am so looking forward to viewing reports ,,, black as with a sprinkling of diamond dust hell yea .

Don't forget the shiney bolts holding the secondary spider and the secondary mirror's edge ( a black texter does wonders here ) , a bit if glare here with both to be eliminated .

Brian.
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  #18  
Old 13-03-2018, 01:49 AM
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Quite a project and well done the only upgrade I would do is to change the tripod to the S/S one , I assume your mount is an EQ3-2 and the S/S upgrade does wonders to the stability, not sure of price in your area but around R 1700 (170 Au dollars) you will notice this better that all the other upgrades you have done
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