Lunt 40 or 50 for full disk imaging?

[Davidm]

I'm considering getting a small scope to allow me to do full disk imaging as a complement to high-res imaging with an LS152 (mosaicing images with the LS152 doesn't really work). I'm basically after something that would allow a quick full disk shot with even on-band performance across the whole disk using my Grasshopper 3 camera (even on-band across the disk being the thing I am really wanting to get right). If I was willing to spend the money, I would go for a Lunt 60 as the best option, but as I just need a decent full disk image and will use higher magnification with the 152, I was thinking 40 or 50 mm will do. For both options, an upgraded focuser would seem to be critical (Feathertouch - though it is only single speed). I am looking to double-stack either option, though the Lunt 40 DS unit is not yet released, so no idea how this might perform. I'll be using a 'spare' B1200 blocking filter (with a KG3 filter replacing the blue glass filter to improve brightness), so at least I don't need to fuss about getting one of those.

The Lunt 40 is attractive due to its price, plus it has a front etalon (presumably this would help with the even on-band performance?). Not sure how double-stacking another tilt-tuned etalon on the front of this might go. I haven't had good experiences trying to DS the LS152, so am a bit leery of doublestacking in a general sense.

The Lunt 50 is a step up in price, and a decent aperture. Not sure how the internal etalon goes with the sweet spot or how imaging would go on this scope in terms of back-focus with an upgraded focuser, etc.

Anyway, interested to hear from anyone with some experience with these scopes and their capabilities. I've seen a few images on forums using these scopes, but they don't seem to be as widely used for imaging as some others.

Cheers,
David

[marktownley]

Have you considered the L60 modular scope - you can buy these without a blocking filter...

[Davidm]

Hi Mark,
I've considered it, but given this would be used almost exclusively for full disk work, I wasn't convinced that it would be worth the extra cost (particularly if I am double stacking). I'm hoping that image brightness would be OK in the smaller apertures for the full disk.

[marktownley]

Hi David.

Image brightness will be fine.

I have the LS50, nice scope, poor focuser, even upgrading to both the moonlite and the the starlight focusers, the issue I had was lack of focus travel. Don't assume the 40 will have more even illumination over the 50 just because it is a front mounted etalon - this would only be the case if it requires zero tilt to be on band.

You might pick up a second hand DS PST for the price range you're talking?

Mark

[Davidm]

Hmm, perhaps neither of these will quite do the trick then. Not sure if a 60 mm would be any different in terms of an even view (or a PST?). Not many options for picking up second hand solar gear in Australia (and even less so out here in the boondocks of Perth), so going down that path ends up with all the drama of buying sight unseen from overseas and hoping there’s no issues during postage.

Any thoughts from people as to what the ideal double stacked, full disk-only setup might be? No single answer for this of course, but want to make sure I consider all options before trying something (or giving up and just make bodgy mosaics with the 152).

[rsfoto]

(or giving up and just make bodgy mosaics with the 152).

Hi David,

How many images do you need in order to assemble a full disk ?

[marktownley]

Have you got somewhere out in Oz you can buy from internally (new Lunt stuff) - and then return if not up to the business?

[EGRAY_OBSERVATORY]

Hi David, from my 11-year experience with my Lunt LS60THaFTBF1200 c/w with the Feather Touch focuser as an alternative to the bulk-standard - was well worth the investment, even at its' relatively high price back in 2010.

Along with it's front DS and also supplied with the LS60CaKFTBF1200 CaK version of the above, was personally delivered to me by the very well known Managing Director of the well known U.K. supplier at the time.

Even though it was delivered to me personally, I Know for sure that Lunt U.S and their European division, will be the currently best method of postal-delivery, as any snags on receipt will be dealt with by Lunt. Their service is second to none and to save for whichever of their products you might wish, you should be very satisfied.

The only banding-issues with my SS or DS-ing has been due to not perfect tuning. I can't vouch for the modular scopes from Lunt, but I would imagine they are excellent under that brand.

You really will get what you pay for - with new SolarScopes with decent warranties, but that may not apply so much with items as 2nd-hand or even via Ebay etc.

As said elsewhere before, "Our Sun will be with us for 'many Moons to come (along with us too) , so saving-up for the best results, is usually the answer to getting the best out of ones dosh."

Terry

[Davidm]

Rainer, the least number of shots for a mosaic without any barlow is four, but I tried it last weekend and it suffered from sweet spot issues. I will keep trying to see if I can get a four-shot mosaic that gets around this, but it is difficult. The next step is to use my 1.5x barlow to get 'inside' the sweet spot a little better, which blows out the number of images needed (maybe 6 or 7). Sometimes I get one image that can't be automatically merged in Photoshop, perhaps because it was taken too long after the first shot, or due to bad seeing. In any case, it gets more and more fiddly, with no guarantee of a decent product at the end (always seem to get a slightly patchy result). That's why I'd like a simple one-shot-wonder.

Mark, there are a couple of Lunt dealers in Australia, but I'm not sure that returning the scope would be an option unless it was actually faulty/damaged and they generally don't have much stock and need to order from Lunt in any case (might as well go straight to Lunt if I want to buy a scope with an upgraded focuser and no blocking filter (plus a touch cheaper going direct as well).

Terry, if I dwell on this for any length of time, I find myself looking at some sort of Lunt 60 as an option, but this is more than 3x the cost of a Lunt 40 in the configuration I am looking at (doublestacked, upgraded focuser, no blocking filter). Using the Lunt website, I think this calculates out to about US$1070 for the Lunt 40, $1665 for the Lunt 50 and $3740 for the Lunt 60). I just have to do a sanity check each time and note that I won't be zooming in beyond the full disk very often, if at all, given the 152 is there I am actually leaning towards the 40 mm option since I will presumably get some sort of uneven on-band performance in any of these (just don't know if any of these might be better than others in that respect). That being said, that 60 mm scope looks pretty good... Here I go again!