Choosing a Large Aperture Solar Scope in the UK

[marktownley]

For next years solar season I have decided to and are looking to buy a large aperture solar scope - it's that one off purchase so I need to get it right. Yes, I have large apertures available with my PST mod but I would like something with that is usable at shorter focal lengths without sweet spotting (the caveat of a PST mod). If I was on the other side of the pond I think I would just get a Lunt100, but over here they charge more in GBP than the ticket value in USD for the Lunt stuff, which is naughty.

When I started to look into this I thought the answer would be straightforward, as a I actually researched it more I found I just got more and more bamboozled with the options, so I thought I would present the facts here and hopefully get the voice of reason from more people! I'm looking at something ~100mm diameter as this seems to be a size I can use on a regular basis with the lovely seeing we have here in the UK. My budget is currently about £4000 - I could generate somemore capital by flogging off some stuff, but I have to be realistic - Mrs Townley wants a new kitchen next year, so that is also an expense I need to bear in mind (also when she see's a new scope has arrived there will be trouble anyway )

First off there is the Coronado Solarmax II 90mm scope with BF15 - at £3799 http://www.telescopehouse.com/acatalog/ ... _BF15.html I think this represents best option in the coronado 90mm range price wise over here http://www.telescopehouse.com/acatalog/ ... s__56.html - the cost rapidly ramps up with larger blocking filters and double stack options. This is a scope i've seen and handled in the flesh - forum member Gary Palmer has one and gets excellent results from it. I also know the lads at Telescope House, infact they supported the Outreach at the International Astronomy Show earlier in the year with myself and Gary, plus i've always been happy with the service i've got from them. I know all the differences with the way these etalons are tuned compared to the (superior) pressure tuned Lunts. TelescopeHouse also have regular 10% off sales which is another tempter...

If we hop into the Lunt camp there are a couple of options : The LS80 with B1200 and basic crayford is going to cost me £3633 (essentially same price as the coronado), going to larger blockers and focuser options starts to top out my budget http://www.iankingimaging.com/show_prod ... tegory=167 - I have to be honest here too, I want to get as large an aperture as possible, and I already have a 70mm scope I can run at Ha. Looking at the Lunt 100 - a lovely scope, I have had the pleasure of being able to use Walters a couple of times now, i'm looking at ~£4999 which is a bit more than i'd like to pay http://www.widescreen-centre.co.uk/Cata ... copes.html

Then over here we have Solarscope on the Isle of Man, of which I have no issues over quality etc, however shop prices are a bit rich http://www.green-witch.com/acatalog/Sol ... lters.html but I do understand that contacting them directly can result in a better deal. Though, I have to say I do think that the 100mm etalon is out of my budget, and as good as they are I don't want to have to drop down to 70mm aperture.

I think the final option I have is the rear mounted Daystar filters. http://www.scsastro.co.uk/manufacturer/ ... ar-filters Here there are choices galore: I could go to a 0.5a quantum se and have the tightest bandpass of all options, or an even tighter bandpass with one of their Ion Ha units... I could even be crazy and get one of their Sodium D filters and end up with a whole new wavelength to explore... I also already have a range of different aperture scopes a daystar could be used on, and at Ha have a range of ERF's already, this lego like interchangeability appeals to me...

Finally (I think!) there is solar spectrum in Germany - another established and excellent filter as used by Andreas Murner, of which, like the Daystar there are options galore for me to ponder http://www.baader-planetarium.com/pdf/s ... trum_e.pdf - again I have all the scopes and ERfs combinations that would be needed.

So there you go! Are there any i've missed out? What do others think? I would love to hear other peoples take and perspective on this, it's a large amount of cash to spend and I want to get it right. Part of me thinks I could plumb for any of the options and be happy...

All thoughts and contributions greatly appreciated!

Thanks,

Mark

[brianb11213]

With due respect, are you asking the right question?

I think you need to think out what you want to do. With your DIY skills, a PST mod (with carefully chosen parts) would probably work as well as anything, for large scale / high resolution imaging of relatively small areas. But I don't like to see Heath Robinson stuff at outreach events ... and a front end large aperture etalon is the way to go for medium res imaging of the whole disc.

The DayStar / Solar Spectrum stuff does look like it is best suited to a dome & slit type permanent installation.

And you do need to bear in mind the seeing limitations of the site(s) you have available.

There's so much more to consider than just the etalon - what else do you want to be able to do with the same scope?

Persistent cloud, jetstream seeing & other commitments on my time are my constraints. Throwing money at hardware wouldn't help solve those. If I were to spend any money on my "solar" rig in the near future, it would be to upgrade my DMK41 to something with a larger chip, most likely no more ambitious than the DMK51 ... I'd gain resolution in my full disk images by being able to throw away the focal reducer.

[marktownley]

This is exactly the sort of response I need Brian 8)

I guess I do need to be asking exactly what I want it to do: I can do my full disks nicely with the DS40 setup i'm using, and for presenting images at web scale it is ideal - it's rare I ever need to present a full disk as a large image eg a poster / print for a wall. I've tried a number of different options for full disks and seem to keep gravitating back to the DS40. The maximum I like to push the 40mm setup is to about f20 (800mm fl) as things start rapidly getting soft and mushy beyond this.

Regards the PST mod I can image to my satisfaction at 100mm aperture and 2000mm focal length, when conditions are excellent I can get up to 3000mm, but this really is the working range of this setup. When I back off with the focal length to 1600mm then I can start to see how the image is going off band and the bandpass widens towards the periphery of the field of view. I'm running a DMK31 so if ran a larger chipped camera this would be more obvious at longer still focal lengths. This is just a constraint within the PST mod and I accept it and know that I just have to work around / with it. I think it is just the perfectionist in me getting frustrated with the limitations with the PST mod. I don't think with the conditions I have getting over 3000mm focal length on a regular basis is going to happen all but a couple of times a year, so i'm not too bothered about these uber long focal lengths (even if I would like to image at this scale - I can't!)

In terms of aperture, 100mm seems to be (for my conditions) a good compromise, I can image most of the time with this. However when I up aperture to 127mm with the PST mod I find I can use this on many fewer days in the year. Clear skies are most definitely a premium, so I don't want to waste what I have 'chancing it' by imaging at too large an aperture and getting cr@pper results out as a result.

I also completely agree with your point about outreach, this is also another important factor, and the general public do feel safer with an 'off the shelf' scope for the sun rather than a home brew jobby. I have been asked numerous times is my setup safe. Answer is yes it is, I would never let people look through something that wasn't anything but safe, however the public are more reassured with commercial scopes.

So I guess, reflecting on this, the void I have in my imaging armament is between 800-2000mm focal length, those mid range focal lengths. Given the options I have looked at, I guess then the daystar / solar spectrum setups would be imaging in the 2000mm+ range, which probably realistically comes back to the Coronado / Lunt setups. I think the solarscope option is just too much cost.

Any thoughts?

[Merlin66]

Mark,
What about Marcello Lugli and his CromixSun filters?
http://digilander.libero.it/malug/

I was in correspondance with Marcello back in 2011 discussing his designs....

[marktownley]

Thanks Ken, i've spotted them before, they kinda remind me of a cross between one of the Beloptik Ha systems and the Omega Optical systems...

[astroshot]

The DayStar / Solar Spectrum stuff does look like it is best suited to a dome & slit type permanent installation.

Agreed.

I previously looked into getting a solarspectrum filter.
The European price at the time was way beyond the US price even allowing for taxes, currency exchange, so be aware of that.
That's why I got a s/h t-scanner - no power supply required for it either.

Also remember the f/30 rule:
2000 divided by 30 = 67mm aperture.
for 100mm aperture, you are looking at 3000mm focal length.

[axle01]

Mark I see the prices you have listed and they seam very high, have you considered ordering direct from the US, I purchase all my large ticket items from the States.

Do you have a set price on import duty and import tax in Pommie land, in Australia it is $1000

Alan

[marktownley]

Thanks fellas. You're right Michael, a daystar or solar spectrum is going to put me right in the focal range the PST mod is in already, or if I drop the focal length I drop the aperture to keep f30 - and I don't want to lose aperture. The only way I think I would consider one of these is if I was considering running at 0.5a or less...

Hi Alan, prices are crazy over here. I found an import duty calculator http://www.dutycalculator.com/new-impor ... lculation/ and tried some figures in there. It does work out a bit cheaper, so I guess that is another possibility.

I see Simon Bennett at the widescreen centre is offering the solarmax II 90mm for £3400 http://www.widescreen-centre.co.uk/Cata ... copes.html - which, at the moment to me has the best bang for the buck...

[JohnW]

Hi Mark, I was interested in your posting. I too have often thought of a 100 mm solar scope and Lunt is probably the best. The price is high so you have to be careful to pick the right scope. I find the problem is actually viewing thru the scopes before you buy. Dealers here in Australia are lucky to have have one solar scope in stock let alone a range for you to compare. It would be great to line them all up and choose once you've been able to compare them. Best of luck - keep us informed.

[Derek Klepp]

Ok I,ll wager in here. First John if you,re ever up at the Gold Coast I can give you a view with the 100 Lunt.Mark out of all the scopes I own I would give them all up bar one the Lunt 100. I did I initially contemplate the 152 but my set up rolls in and out and occasionally I take my scopes on holiday.Hence two 100mm EDs sit OK on a HEQ5 .I can interchange the WL and CaK Wedges and thus all things are on the same scale.The Daystar filters really are the Bees Knees for close ups just look at Randy,s pics but the better units do have temp control. I think Nando(where is he?) achieved superb results with the 0.4Daystar Ion unit and a 127 mm aperture .His setup would be transferable between apertures but again depend on a long FL.
If it comes down to outreach the 100 Lunt really fits the bill or the Coranado units(there are a lot of members producing good images with there 90mm setups) but it is 90mm.
My final reason for purchasing the Lunt was on reading Stephen,s reviews and asking his personal opinion as he looks through everything and has to setup and pull down hundreds of times a year.I bought cold turkey so it was a risk.And after forking out $3000 aus for a Daystar Solaredi unit I was hoping the view through the Lunt would be at least 3 times better. It was far more than that it took my breath away.So good is that view that I have not even upgraded my camera as I am happy with what I see as liveview is my main aim. With your processing skills and the DMK 31 I think your images with the Lunt 100 would be very good indeed.
Perhaps Mark being a teacher and using the scope for outreach you can get a tax concession.Out here some schools are going down that track.You can always come down here for a holiday and try mine for a week.We could hook up with Matt in Brisbane who has the 80mm then go to Cairns and compare with Ralph's Coranado,s.
Cheers Derek
PS I am still contemplating a DS unit for the 100 or a Daystar Ion .4A unit.

[marktownley]

Hi Derek, I would love the 100m lunt, but it's nearly a third as much again compared to the 90 and i think the budget (short of a lottery win) is going to be the governor here. The narrow bandwidth daystars produce some fantastic results like you say - I want one of those too! Doh!

Regards the tax thing, we still even have to pay the VAT on stuff if it's bought via the school (even if it is for the school) - our government doesn't miss any tax opportunities sadly...

[swisswalter]

Hi Mark


a great thread. You are doing a great job on full disks with the 40 mm, so there is really no great gain doing the same with a LUINT 100 and a big chip.

leaves you with the big opening doing close ups. There you have already your PST mod which works on almost every opening. I think you have an 70 mm and 127 mm refractor. What you may be missing is a 0,5 daystar with 6" lens and a TZ3 or 4 on a 6" refractor.

Unless you start to do an outreach ever week you do not need a dedicated 90/100 mm solar scope.

Sorry to spoil the sunday ;-)

[marktownley]

Hi Walter,

Yes, the 40mm does the business with the full disks, that's going to remain doing that job.

The PST mod is a great interchangeable filter - i can get it to work on my 40,70, 100 & 127mm scopes if I need to

I guess the gap I want to fill is the 800-2000mm fl range hence me thinking a SM90/LS100. However yes, you are right a tight bandpass for Hi-res closeups would also be desirable. Problem is I can only get one scope... I bet if I could afford 2 I would want 3, it's always the way :whistle:

[swisswalter]

Hi Mark


I feel so much with you, I went through the whole thing my selve, without buying to many pairs of shoes ;-) please keeep that for your selve :whistle:

Sorry , I still do not see your exact needs. If you wish to capture the sun from 800 to 2000 m FL you could just get a blocking filter and a SM90 external etalon . That would not be the world , wouldn't it?



.

[swisswalter]

Hi Mark

an Addition please


You are doing a such great job on full disks, so forget about upgrading your equipment on that side.

You are going to gain very, very little compared to the investment you would go into

[marktownley]

Sorry , I still do not see your exact needs. If you wish to capture the sun from 800 to 2000 m FL you could just get a blocking filter and a SM90 external etalon . That would not be the world , wouldn't it?

Yes, an external etalon like the SM90 would work too, that's another option.

[Montana]

Mark, you seem to me a guy who loves taking full discs, I think a Daystar or Solarspectum would only give you good high res images which you already can do with your PST mod.

Now Solarscope 100mm is £6,500 direct from Ken. If I were you I would go for the Coronado 90mm which I think gives just as good images, see Alan Friedman then you can take full discs to your hearts content

Alexandra

[marktownley]

I guess the thing i'm trying to achieve in Ha is having a full range of focal lengths to be able to image at; I can do this in both wl & CaK from 3000mm, but in Ha I can only do each end of that focal range. When seeing isn't good I end up falling back to the full disks, and it would be nice to be able to push the focal length a bit more in these situations and get some higher res quadrants to complement the full disks, which isn't possible with the PST mod without dropping back in aperture too...

[swisswalter]

Hi Mark

I still can't see your point. May be you just need something like a SM90 and a blocking filter

[MapleRidge]

Hi Mark...

Choosing your filter is like the bride and I trying to find common ground in the kitchen/bath renovation we have started to plan for hmy:

The PST mod works amazingly well (your shots are proof of that), but the need for f10 puts a squeeze on the aperture/focal length equation, and still suffer the sweet spot issues.

The full solar scope from the likes of Lunt/Coronado give the benefit of even field illumination and a moderate focal length (say LS100 with 800mm fl). When seeing is less than desirable you can run at prime focus or add a 2x barlow. When conditions are good, you can go wit the 2.5x, 3x, 4x, 5x and have enough aperture to support it.

As another option, and as a modder you should be able to nail this one), do up a mod with the Lunt PT etalon (DSII or cannibalize a LS60 for parts) and add them to a used 100mm f7 OTA. Lots of used OTA's out there...Orion, Stellarview, Celestron, etc...add in the ERF and machine an adapter to mount the etalon and you should be able to work with 100mm (or more) aperture and employ the same barlow system to match the focal length to the conditions. Based on my system, you will have a sweet spot, but you have a full disk system now...so long as you don't use a massive chip you will get along fine at the lower end of the focal length range.

If I had to do my mod over again I'd put it on a 110mm or 120mm f7 donor OTA.

Just my thoughts,
Brian

[marktownley]

May be you just need something like a SM90 and a blocking filter

I'm tempted by this idea Walter, but I would have to get a new OTA to mount it on too.

I'm in the process of super-modding the Tal100R refractor I use for my closeup Ha, CaK and WL work; first off i'm replacing the stock focuser with a Moonlite - having to do some machining at work as the collar on the Moonlite is larger than the diameter of the scope tube. Secondly i'm making a cell to permanently mount the tri-band ERF internally in the scopes tube and thirdly it will need a sol-finder on it... I intend this to be my hi-res multi wavelength scope

[Merlin66]

Mark,
I agree 100% with Walter!
If I was spending you money, that's the way I'd go...you could always add the SM90 to the front of your PST mod for double stacking!!!

[MapleRidge]

Hi Mark...

I've noticed your reference to the tri-band ERF on a few occasions.

Can you share any details on this type of ERF...even if you don't let the cat out of the bag, it needs a few holes poked in for air

Brian

[marktownley]

Hi Mark...

I've noticed your reference to the tri-band ERF on a few occasions.

Can you share any details on this type of ERF...even if you don't let the cat out of the bag, it needs a few holes poked in for air

Brian

Here you go Brian http://www.ebay.co.uk/itm/85mm-ERF-Ener ... 1312174583? It is Oliver from Beloptik who is selling them. Not many left though now!

[Montana]

If it were me, like I said before, I would buy the Coronado 90mm, you could fit it on your 127mm. Then you can take fantastic full discs, double stack it with your PST mod if needed and if you need high res, you would use your PST mod anyway at 127mm.

Alexandra

[marktownley]

Yes, the external 90 is a possibility, but a new ota would be needed, let me explain why.

The tri-band ERF arrived today (a fine piece of glass! 8) ) - this will be mounted internally in the 100mm Tal. When fully pimped the idea with this scope is simply by changing the filters in the focuser I can switch very quickly between CaK, WL & Ha all at the same image scale. The Tal really is fine optically and punches above it's weight I think when you consider its price (£249). I don't want to put an external 90 on this I would have double ERFs and that equals longer exposure, so would mean another scope - ideally a decent 100mm f6/7, this would a rely on picking up a 90mm etalon at a decent price... decisions decisions!

[swisswalter]

Hi Mark

If that helps. I have about 8 scopes for sale ;-) Just come around and have a look ;-)

[marktownley]

Can you thread a Coronado 90 onto the end of any of them?

[swisswalter]

Hi Mark

no problem at all if you have your skill