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Mr niall

The aim; super cheap white light setup

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Hello there

I'm trying to create the worlds cheapest white light solar setup. I'd toyed with the idea of getting the astromedia solar projector which looks quite cute and seems to work looking at the reviews but then was wondering if there was any fundamental reason why the heritage 76mm with a baader film wouldn't work equally well?

https://www.firstlightoptics.com/all-telescopes/skywatcher-heritage-76-mini-dobsonian.html

Or am I missing something obvious as I cant see anyone has ever actually tried it. I'm aware the people have done it on the 114p virtuoso so I guess its feasible. I'd really like to get into tracking and sketching sunspots so I'm thinking a classic projection setup may be fun but not quite have the resolution I'd need for quality sketches?

Sorry if these are daft questions, solar really is a completely new area to me.

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I would have thought that the Heritage 76 would work okay with a Baader filter. Make sure you remove the finderscope or cover it up.

The  projection method can be a simple setup, if you have a refractor, making sure you don't melt your eyepiece which I did.

I have used a solar projector to view the Venus Transit in the United States - see below. Really good image but these devices are about £200. I accept the Astromedia could be fun making and testing.

My preferred option would be the Heritage 76.

sunspotter.JPG

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Projection setup might be better for any sort of measurement and "precision" sketching - you put a tracer paper and then you draw "to template".

Regular observing is going to allow you to sketch, but in the same way one might be sketching the Moon and planets - there will be some skill involved there to get decent rendition.

Although Heritage 76 is probably good basis for the cheapest WL setup, I'm not sure it would be my first choice. What you save on scope and filter, you will probably loose on eye pieces / barlows. In order to have decent view of the Sun, you will want to start with something like x60 power for full disk and go upwards for detail (you need something like x100 up to see granulation). With 300mm scope that means 5mm FL ep and "lower" (or addition of barlow).

About same aperture (hence resolving power) will give you this scope:

https://www.firstlightoptics.com/evostar/sky-watcher-mercury-707-az-telescope.html

and it would be even better if you could find 3" F/13 or something like that for such work. Maybe see if you can get a second hand refractor with such specs (doubt you will find a new model with such specs that is going to be in "cheap" category).

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53 minutes ago, Mark at Beaufort said:

The  projection method can be a simple setup, if you have a refractor, making sure you don't melt your eyepiece which I did.

 

49 minutes ago, vlaiv said:

Projection setup might be better for any sort of measurement and "precision" sketching - you put a tracer paper and then you draw "to template".

Thanks - as feared there appears to be lots to consider!

I will admit that projection would be a more appealing route if it offers a similar resolution to just viewing through baader film straight to the eyepiece.

but I must admit I am a little nervous about the whole “pointing a scope straight at the sun” nature of it. Is it not a little bit dangerous?  In my naivety and accident prone history I can’t help but feel that there’s a relatively high chance of me injuring myself or burning down the neighbourhood. I’ve accidentally started a fire with an uncapped 6x30 finder before and it was fairly frightening! And there’s kids and dogs at home that will no doubt “get involved”. Or have I misunderstood the projection concept?

Theres an evostar 90 Ota with diagonal and eyepieces on astroboot for £75 at the mo - do you think that’s more the sort of thing I should look at?

apologies again for the daft questions!

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VIEWING THE SUN IS POTENTIALLY VERY DANGEROUS! Apart from all the other potential problems and faffing about the projection method uses an unfiltered solar image. If one of the children, pets or careless adults just happened to get their eye to the eyepiece.........:excl: 

The Solar film method is 100% safe. Mark's link is excellent. However, whilst I do not wish to discourage anyone from making thier own solar filter, if one is feeling a tad nervous about the whole business there are safe and affordable solar filters available from tip-top dealers like FLO :thumbright:. Just make really sure no one looks at the sun directly, which is tempting when viewing with a scope.

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If you go along the projection method make sure you stay with the scope 100% of the time especially if children are around. When I was in the United States for the Venus Transit I was setting up my PST on a tripod and had a separate 90mm Refractor on another tripod for projection. I had not pointed the refractor towards the Sun when a youngest came behind me and looked, before I could stop him, straight into scope. If I had set up that scope first he would have been blinded - hence my statement above.

Personally I would prefer to observe the Sun with a solar filter and have always purchased mine from an astro dealer.

 

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Thanks all - I think that probably confirms the niggles I had about using a scope as a projector, I think I’ll probably steer my ideas back to the safety of either a filtered scope or a traditional projector.

now... small frac or small reflector 🤔🤔

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5 hours ago, Mr niall said:

Theres an evostar 90 Ota with diagonal and eyepieces on astroboot for £75 at the mo - do you think that’s more the sort of thing I should look at?

 

3 hours ago, Mr niall said:

lovely looking scope - that might be just the ticket. 

I would rather go for 90mm of aperture and 900mm focal length than a smaller scope, but second hand one is OTA - which means you will need to mount it somehow. If you already have suitable mount - I think it is better option.

Main problem with such a cheap small refractor is going to be diagonal. Focuser is not going to be very good either (although usable) but there will be no difference between dob focuser and this one (in terms of quality). Diagonal is likely to be usable at best. Newtonians do have secondary mirror so no need for diagonal, and it is very likely that secondary is going to be of a better optical quality than cheap diagonal, so that is a plus for Newtonian.

There is option that will bring best views in WL and solve diagonal in the same go - but it is expensive. It is herschel wedge - special kind of diagonal that passes only small percent of light (around 5% and it is equipped with additional neutral density filter). It gives sharpest WL views, but can only be used on refractors (which is probably better choice with such small apertures). When using this herschel wedge you don't need baader solar filter - it does all filtering you need (just make sure ND filter is included with wedge).

But, like I've mentioned - it is fairly expensive piece of kit - it can cost more than scope it is being used on. I have this one and it is fairly good:

https://www.firstlightoptics.com/solar-filters/lunt-white-light-herschelsolar-wedge.html

You can couple it with polarizing filter, because light coming from the wedge is already polarized and additional polarization filter screwed on EP can be used to "tune" amount of light for comfortable viewing (and best contrast) - just rotate EP for desired light level before you tighten it in diagonal.

 

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Posted (edited)
2 hours ago, vlaiv said:

 

I would rather go for 90mm of aperture and 900mm focal length than a smaller scope, but second hand one is OTA - which means you will need to mount it somehow. If you already have suitable mount - I think it is better option.

Main problem with such a cheap small refractor is going to be diagonal. Focuser is not going to be very good either (although usable) but there will be no difference between dob focuser and this one (in terms of quality). Diagonal is likely to be usable at best. Newtonians do have secondary mirror so no need for diagonal, and it is very likely that secondary is going to be of a better optical quality than cheap diagonal, so that is a plus for Newtonian.

There is option that will bring best views in WL and solve diagonal in the same go - but it is expensive. It is herschel wedge - special kind of diagonal that passes only small percent of light (around 5% and it is equipped with additional neutral density filter). It gives sharpest WL views, but can only be used on refractors (which is probably better choice with such small apertures). When using this herschel wedge you don't need baader solar filter - it does all filtering you need (just make sure ND filter is included with wedge).

But, like I've mentioned - it is fairly expensive piece of kit - it can cost more than scope it is being used on. I have this one and it is fairly good:

https://www.firstlightoptics.com/solar-filters/lunt-white-light-herschelsolar-wedge.html

You can couple it with polarizing filter, because light coming from the wedge is already polarized and additional polarization filter screwed on EP can be used to "tune" amount of light for comfortable viewing (and best contrast) - just rotate EP for desired light level before you tighten it in diagonal.

 

All good points sir, but I think we may be drifting away from the original aim which is to get up and running as cheap as physically possible. The way this conversation is going, I believe by the time this thread has run it’s natural course I’ll be purchasing a Quark to go on a Tak100 and mounting it all on an eq6... 😜

The 707 frac you showed me is very nearly twice the price of the mini dob - but from what you suggest I think it will provide double the experience so that’s ok. After that, well we’re getting into diminishing returns territory. If I enjoy it I’ll probably get a solar scout or PST as they look like a lot of fun but that’s some way down the road and I kind of just want something as cheap and straightforward as at all possible at this stage...

Edited by Mr niall
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Just an update - ended up buying a skywatcher mercury 607 (60/700) on an AZ2 with finder, 2x eyepieces and barlow that I found brand new on ebay for £48 , and an explore scientific white light filter for £18. So £66 spent so far...

Will report back.

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