150mm Solar Newtonian first light

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Martin_S
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150mm Solar Newtonian first light

Post by Martin_S »

Here is my first solar newtonian that I converted from an old 150mm f/8 that was well past it's use by date. I was hoping to build a Serrurier truss, but didn't have enough parts on hand as we are in lockdown and couldn't go out. The primary mirror was left in hydrochloric acid for 3 days to remove the coating.I did a quick collimation to test everything , then took a six pane mosaic at prime focus with my ASI174 mm. The seeing was not good enough for any high res imaging as the atmosphere was on the boil.

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H alpha : ,Skywatcher 120mm F8 open frame refractor, a tilted 2" 7nm H-alpha filter as a sub energy rejection filter, Baader TZ4 telecentric focal extender, Player One energy rejection filter, Combo Quark Chromosphere, Naked PST etalon for double stacking, ASI74mm camera
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Re: 150mm Solar Newtonian first light

Post by rsfoto »

Hi Martin,

Very nice. So taking off the coating makes the mirror work in the same way as a Herschel wedge ?

Thanks Rainer


regards Rainer

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Re: 150mm Solar Newtonian first light

Post by Martin_S »

Hi Rainer, it sure does, I'm impressed with the results , it outperforms my 150 maksutov as the air flows through the truss so there are no tube currents etc.

Martin


H alpha : ,Skywatcher 120mm F8 open frame refractor, a tilted 2" 7nm H-alpha filter as a sub energy rejection filter, Baader TZ4 telecentric focal extender, Player One energy rejection filter, Combo Quark Chromosphere, Naked PST etalon for double stacking, ASI74mm camera
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Re: 150mm Solar Newtonian first light

Post by thesmiths »

The primary mirror was left in hydrochloric acid for 3 days to remove the coating
Ferric Chloride will etch the aluminium coating off of a mirror in three hours or so. I believe it is also a bit less nasty to dispose of (mix with bicarbonate of soda to neutralise it). See my post from a few years ago: viewtopic.php?f=9&t=11814&p=117999&hilit=ferric#p117999 and a more recent one by Bart viewtopic.php?f=9&t=25766


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Re: 150mm Solar Newtonian first light

Post by Martin_S »

thesmiths wrote: Mon Dec 20, 2021 11:50 pm
The primary mirror was left in hydrochloric acid for 3 days to remove the coating
Ferric Chloride will etch the aluminium coating off of a mirror in three hours or so. I believe it is also a bit less nasty to dispose of (mix with bicarbonate of soda to neutralise it). See my post from a few years ago: viewtopic.php?f=9&t=11814&p=117999&hilit=ferric#p117999 and a more recent one by Bart viewtopic.php?f=9&t=25766
I tried getting some ferric chloride locally, but could only get it on Ebay or mail order. I just used some of my pool acid, and added some bicarbonate of soda to neutralise it. Thanks for the links, they are an interesting read.

Martin


H alpha : ,Skywatcher 120mm F8 open frame refractor, a tilted 2" 7nm H-alpha filter as a sub energy rejection filter, Baader TZ4 telecentric focal extender, Player One energy rejection filter, Combo Quark Chromosphere, Naked PST etalon for double stacking, ASI74mm camera
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Re: 150mm Solar Newtonian first light

Post by marktownley »

A great scope mod there Martin! Thanks for sharing.


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Re: 150mm Solar Newtonian first light

Post by Martin_S »

Thanks Mark, Have a great Christmas and new year,

Martin


H alpha : ,Skywatcher 120mm F8 open frame refractor, a tilted 2" 7nm H-alpha filter as a sub energy rejection filter, Baader TZ4 telecentric focal extender, Player One energy rejection filter, Combo Quark Chromosphere, Naked PST etalon for double stacking, ASI74mm camera
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Re: 150mm Solar Newtonian first light

Post by marktownley »

Thanks Martin, you too.

I've always liked the idea of a solar newton.


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Re: 150mm Solar Newtonian first light

Post by thesmiths »

My recommendation for a scope from which to build a solar Newtonian would be the "Sky-Watcher Heritage-150P Flextube Dobsonian Telescope". The brilliant thing about the Flextube design is you can shorten the length easily to increase the back focus (the secondary mirror is oversized enough to accommodate this). It also has quite a nice 3-arm secondary mirror spider support. The mirror is parabolic (in theory better than spherical). It has a Vixen dovetail on the side so it is easy to attach to all kinds of mounts. The included Dobsonian mount is actually very useful and can be used with many other telescopes. I based my solar Newtonian on the 130P Flextube (because it was so cheap), but if I had to do it again, I would use the 150P.

The focal length is 750mm (f5) so is short enough to get a full disk on a large sensor, and you can use a magnifier to get up to f10. In theory, you can use a (homebrew) CaK filter, although seeing will be an issue with such a large aperture. Collimation is also a bit tricky and I think poor collimation is the reason why some solar Newtonians don't live up to expectations.

If you do get one of the Flextubes, don't forget the Teflon tape for the rotating focuser (otherwise it's a bit too loose).


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Re: 150mm Solar Newtonian first light

Post by Martin_S »

thesmiths wrote: Tue Dec 21, 2021 5:43 pm My recommendation for a scope from which to build a solar Newtonian would be the "Sky-Watcher Heritage-150P Flextube Dobsonian Telescope".
These scopes are amazing for the price, they get snapped up pretty quick on the used market over here.

Two weeks ago I bought an old EQ3 pro for $100 with a 150mm f8 OTA that also included a big box of accessories ,eyepiece's, battery and charger .
I only wanted the tripod for my AZGTi , so I was stuck with all the other stuff.

I rebuilt the mount, it works fine and converted the OTA into a solar Newtonian. this must be the bargain of the year for me.

Martin
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H alpha : ,Skywatcher 120mm F8 open frame refractor, a tilted 2" 7nm H-alpha filter as a sub energy rejection filter, Baader TZ4 telecentric focal extender, Player One energy rejection filter, Combo Quark Chromosphere, Naked PST etalon for double stacking, ASI74mm camera
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Re: 150mm Solar Newtonian first light

Post by OlegLviv »

Hello! Great job!
I saw this telescope in the book http://solar-astronomy-book.com/


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Re: 150mm Solar Newtonian first light

Post by DavidP »

How would one adapt such a project to Ha?


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Re: 150mm Solar Newtonian first light

Post by Martin_S »

DavidP wrote: Sun Jan 30, 2022 5:20 pm How would one adapt such a project to Ha?
Interesting question David. Maybe a PST mod or a quark . I'm not sure what the illumination would be for Ha .

Martin


H alpha : ,Skywatcher 120mm F8 open frame refractor, a tilted 2" 7nm H-alpha filter as a sub energy rejection filter, Baader TZ4 telecentric focal extender, Player One energy rejection filter, Combo Quark Chromosphere, Naked PST etalon for double stacking, ASI74mm camera
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Re: 150mm Solar Newtonian first light

Post by vineyard »

Thank you for this thread - I just found it & its got my mind whirring. Before lockdown I was taking ATM classes to make a 6" newtonian. The mirror is almost finished but not aluminised - and I no longer need a 6" newt for night-time - so a seed has truly been planted! Is there a good book I can read to brush up on this (that solar-astronomy-book.com) or would the best thing be to soak up all the Solar Newtonian pages here? Thanks again!


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Re: 150mm Solar Newtonian first light

Post by Martin_S »

Hi Vineyard , thank you for your comment. The Solar Astronomy book is an essential reference for all aspects of solar astronomy. I would advise you to do as much research on a 150mm solar Newtonian as possible. A 150mm telescope is a great instrument but you must familiarise yourself with all the safety requirements associated with an instrument this size and strictly adhere to them.
A 150mm solar scope's performance is very dependant on atmospheric conditions, my 102 f10 refractor gets more use than the 150mm Newtonian as I am in the sub tropics at sea level about half a Kilometre from the ocean. I hope this has helped with your prospective white light endeavour.

Martin


H alpha : ,Skywatcher 120mm F8 open frame refractor, a tilted 2" 7nm H-alpha filter as a sub energy rejection filter, Baader TZ4 telecentric focal extender, Player One energy rejection filter, Combo Quark Chromosphere, Naked PST etalon for double stacking, ASI74mm camera
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