Recommend me solar and Ha filters for my scope.

[bloodhound31]

Hi guys,

Just trying to get some ideas from those who already image with these filters for the sun, what to get for my scopes. So far I have only used Baader film.

One option is to get Ha filters for either my Skywatcher ED80 or ED120.

The other is to buy a solar telescope. If I do this, what's the difference between buying a 60mm or a 90mm?

Can I use my Orion DSI one-shot CCD camera, or is it better to use my Canon 5DII?

Can anyone provide some informed advice on them and recommend some?

Baz.

[casstony]

Given the small cost differential between the Ha scopes and Ha filters you might want to consider buying a whole Lunt scope rather than the filter and adapter.

[bloodhound31]

Thanks Tony,

Anyone here got some example shots from a Lunt scope?

Baz.

[bloodhound31]

I've been looking at the Lunt and Coronado scopes. Very confusing stuff.

[casstony]

The Lunt pressure tuned scopes have the advantage that the etalon is always perpendicular to the incoming light, rather than being tilted for tuning. This tends to give a larger sweet spot and makes double stacking much easier down the track.

Matt Wastell has some images with the Lunt 60 scope here: http://www.iceinspace.com.au/forum/showthread.php?t=91941

[bloodhound31]

Hey thanks mate! Had a look at Matt's stuff. Yep, I just got more fired up.

What does all that stuff about pressure tuned, etalon, and double stacking mean? I have no idea whatsoever.

Baz.

[casstony]

The etaon is the primary filter near the front or middle of the scope which lets through a narrow band of light (less than an angstrom), but does so at many points across the spectrum. The blocking filter at the rear of the scope filters out all but the single peak needed for Ha observations.

Most Ha scopes/filters are tuned by mechanically tilting the etalon to bring it 'on band', while Lunt also produces etalons which are tuned by varying air pressure in a chamber surrounding the etalon. Changing the air pressure allows the etalon to be kept in the ideal perpendicular position relative to incoming light.

Double stacking refers to putting a second etalon in front of the first one, reducing the passband from about 0.7 to 0.5 angstroms and increasing the amount of detail seen on the solar disc.

[bloodhound31]

That's a little clearer Tony, thanks mate.

So is the air pressure changed by the volume of air in the tube heating up as you observe? Does the pressure tilt something mechanically, like an element of glass?

Have I understood you right?

Baz.

[casstony]

No worries Baz. There's a brass cylinder on the side of the scope which is screwed in or out to change air pressure. AFAIK, the etalon is static and there's something about how the air behaves at different pressures relative to the light which causes the tuning to happen. There's definitely no tilting in a pressure tuned filter.

The imaging guys must be asleep or on holiday - I'm sure they'll turn eventually :)

[bloodhound31]

Ah that makes it clearer mate.

Thanks very much Tony. Now to just find one of these darned programs that will stack my CR2 files of the Venus Transit...... :mad2:

Baz.

[dannat]

Barry if it were me I'd be buying one of the solar filters like this (http://www.thousandoaksoptical.com/halpha.html) from t/oaks, the PST is only 40mm,
the filters will strap on your ed80 & you'll have be able to img, the PST needs to be modified, the other solar scopes are fairly expensive & you'll have another scope sitting around rather than just the filter

[bloodhound31]

Thanks Daniel. That is an interesting avenue.

After reading it, it looks like it would cost me close to $1000 to buy the combination I need for my ED80. For another $500 I can buy a scope purpose-built for imaging. :D

I had a flick through the link you provided and browsed their image gallery. (http://www.thousandoaksoptical.com/photo.html) I don't know if it was the quality of the filter setup or the skills of the photographer, but the images on their site don't impress one wanting to image the sun. :shrug: Actually considering they were taken through a 14 inch telescope, I'd go so far to say that they are woeful. And this is their product advertising? Fail.

As far as having another scope sitting around, I'm sure the new observatory will have plenty of room!!! :D :D :D

[naskies]

With some manufacturers, the blocking filter included with the full-scope kits are smaller than what you get buying just the solar filter for use on an existing scope. I believe that's how they keep the prices so similar (though I may be mistaken).

[casstony]

The reason the Ha scopes are not more expensive is because they are able to use a smaller internal etalon than front mounted filters. The etalon inside the Lunt 60mm scope is 35mm in diameter, but you still get equivalent performance to a 60mm front mounted filter.

I've compared the 60mm pressure tuned Lunt scope and their 50mm front mounted filter and the contrast and detail was best in the 60mm scope. The scopes are better value imo since you can get more aperture for your money.

[bloodhound31]

I'm beginning to understand somewhat.

What about a 60mm solar scope vs a 90mm? Is it like normal scopes where bigger is better?

What does this do at the back end? Like my ED80 vs my ED120, The 80 is able to image full disk, where as the 120 can't get the whole disk in. Will a full frame sensor on my 5DII still capture the full disk of the sun on the Solar-60 and/or 90? Will a cropped sensor on an Orion DSI start cutting into the limb of the sun?

[Poita]

It is a bit like planetary, a bigger aperture can reveal better detail, but seeing can often mean you see more in the smaller scope.

I have a 60mm PST and have done an 80mm mod also and get views as good as any Lunt 60 I have seen, but for photography the sweetspot is wider in the Lunt, so it may be a better choice.
The 90mm scopes are *serious* money.

Yes the focal length goes up with aperture so you get less of the Sun on the CCD.

You may want to go over to Solarchat and have a chat, lots of Solar scope owners over there.
http://solarchat.natca.net/index.php/en/

[sheeny]

G'Day Baz,

Just for reference, check out any of my solar stuff for the last year or so, and you'll see what your ED80 could achieve with a Coronado SM40 on the front and a Lunt B1200 blocking filter. I'm not aware that there;s any visible difference in the quality of images from either the Lunt or Coronado stuff. They're both pretty good gear.

If you are a setup and tear down astronomer, or you are going to specialise in solar work, a solar scope is the way to go. I am still following the filter route as this allows me to use my ED80 in the obs without changing OTAs and rebalancing the mount (hence I preserve all my EQMOD sync points:thumbsup:). i.e. better pointing, and less hassle.:) I am in the process of buying a Lunt LF60 full aperture filter to replace the SM40 even though the filter is more expensive than the scope!

Another reason why the solar scope are cheaper is they only need basic optics. With narrowband Ha you don't need to worry about chromatic aberations, etc.

I will say I am very happy with how my ED80 performs with my Ha filter. It has very flat and uniform illumination and no evidence of a sweet or hot spot.:thumbsup: My only limitation with the SM40 filter is due to aperture I feel. I struggle to get sharp images when I throw a 2.5x powermate in the train because I'm exceeding the resolution of the filter (hence the step up to 60mm).

Al.

[bloodhound31]

Thanks Peter and Al.

Al, where can I find your photos through your filtered ED80? Could I trouble you to post a picture of your setup?

Baz.

[sheeny]

Lets see if this works, Baz:

http://www.iceinspace.com.au/forum/search.php?searchid=2163947

If not, in the IIS advanced search page enter:
User Name: sheeny
Threads started by user
Images, Solar system

That should get all my solar stuff.

I think you'll find the full disc shots are nice sharp, while my hires Ha stuff goes a bit soft. A larger aperture filter/scope will allow higher magnification/resolution before it goes soft (seeing permitting).

Al.

[bloodhound31]

Yep, there's definitely some nice images there Al. I had a look at a lot of them and it looks like you have a country mile since first light. I couldn't find a pic of your rig though.

Baz.

[sheeny]

That's probably because I don't have a current one. I thought there might be enough detail of the solar rig on the ED80 when I shot my spectroscope set up, but no. I'll have to take some new shots. Unfortunately, ATM the weather has gone real bad again, so it'll have to wait for a fine day.

FYI I have my ED80 and C11 side by side on my NEQ6. The L200 spectroscope is on the C11 with a modified flip mirror/beam splitter on the C11 so I can image or use the spectroscope and guide.

Al.

[Derek Klepp]

Baz I started off with a 60mm scope and now have a 100mm Lunt. The eyepiece views are astounding.In all honesty a 60mm scope would be a good entry point or 60mmPre-filter + a blocking filter for your current scope.Like anything you get aperture fever but after 100mm portability comes into it. If you intend to image good results can be had from any scope.If you trawl through the forum sections you will see many pics with many scopes. Paul Hease, Peter Ward and Al have Coronado Variants while Matt Wastell,Ted an myself have Lunts, and others PSTs(Coronado).My only recommendation is that if at all possible have a look through one first.Also as advised you may want to check out the Solarchat site .
Hope this helps a bit.
Derek

[barx1963]

I recently had the opportunity to see my Coronado SM60 side by side with the SM90. The 90 is a big beast, if portability is any way important and you go the dedicated solar scope road, and you go Coronado rather than Lunt, the 60 is the go.

Malcolm

[bloodhound31]

Thanks a lot gents.

Portability is the least of my concerns as I'm a big strong lad, plus it will probably be going in the observatory and stay there.

I think I need to weigh up the trade-offs between budget and image quality.

Bless ya's!

Baz.

[Paul Haese]

I have just gone through this process again as I am upgrading from my 60mm to a larger scope. I decided on a 80mm Lunt but still have reservations on if I should get a 100mm but I cannot be assured of having it by the eclipse.

What I found is that prices for filter sets are more costly over a certain size rather than a dedicated scope. As pointed out it has a lot to do with full aperture etalons rather than narrow etalons in dedicated scopes. Basically buy the biggest you can afford, but I reckon by a dedicated scope.

The other thing is that Ha light is monochromatic. That being the case you need a monochrome sensor for imaging. Using a colour camera on a monochrome system is pretty much a waste of time. You need to do a lot of work to get good images and these images will never be as nice as those produced by a mono system.

With Ha imaging you don't need to have double stacking to get great detail. For viewing double stacking can make a huge difference unless as Dereck has pointed out that you have a 100mm scope.

[Poita]

I would check out the SMF90 and BF15 package, it gets you 90mm of aperture and you can currently pick it up in the states with shipping included for USD$2900.
Add another 300 for GST and that brings you in at well over $1000 less than the Lunt LS80, and you can get it now rather than waiting.
Worth a look if you already have a refractor of 80mm or larger. That $1000 saved can go towards a PGR mono camera.