Questions about 90mm mod to Lunt LS50THa by Great Attractor

Frankenscope? Let's see it!***be advised that NOTHING in this forum has been safety tested and you are reading and using these posts at your own peril. blah, blah, blah... dont mess around with your eyesight when it comes to solar astronomy. Use appropriate filtration at all times...
Post Reply
User avatar
Radon86
Almost There...
Almost There...
Posts: 779
Joined: Sat Mar 23, 2019 10:05 pm
Has thanked: 745 times
Been thanked: 660 times

Questions about 90mm mod to Lunt LS50THa by Great Attractor

Post by Radon86 »

Great Attractor: 90mm aperture: Lunt LS50THa modification to 90mm aperture: solar chatforum article: viewtopic.php?f=9&t=19238


Dear Solar Chatforum/Great Attractor,

As of 22nd March 2021, from sunny London.

Hi, I am hoping to get some help with regarding building a modified scope like Great Attractor's Lunt LS50Tha modification to 90 mm aperture.

I had a little difficulty understanding all the technical details, so I summarise what I understand. Please correct me on any mistakes !

1) The reason for this modification is to get increased resolution from a 90mm optical lens compared to a 50mm lens, increased contrast and optical performance for imaging of sun surface and proms.
2) Components of this modified scope are (from front to back):

a) The 90 mm Baader D-ERF
b) the donor OTA body of Celestron SkyScout Scope 90 (http://www.teleskop-express.de/shop/pro ... Scout.html) – f/7.33. Basically the metal tube and the 90mm objective lens
c) Donor OTA adaptor (not sure of where this is, or dimensions)
d) extension tube of 49mm length (M68)
e) Coronado BF15 converted to straight-through configuration - for surface imaging of sun (lunt BF600 for imaging of proms can be used)
f) Barlow 1.6x (to obtain better sweet spot focusing)
f) ? Borg helical focuser
g) Camera - PGR Chameleon 3 mono (ICX445)
h) Mount : HEQ5-Pro
i) Laptop+ software

Basic cost (excluding camera and mounts and computer hardware+software): at current prices:

Original Lunt LS50THa: £1329 (https://www.firstlightoptics.com/lunt-s ... scope.html)
Baader front D-ERF 90mm £345 (https://www.widescreen-centre.co.uk/baa ... lters.html)
Celestron Skyscout 90mm OTA = approx ? £150
Coronado BF15 = unable to find this, ? on widescreen centre, a B1200 filter for 1.25inch or 2 inch diagonals is £924, for B1800 it is £1424 (https://www.widescreen-centre.co.uk/blo ... cuser.html)
Borg helical focuser ? 1.25 inch focuser from Rothervalleyoptics = £59 (https://www.rothervalleyoptics.co.uk/zw ... r-125.html)


Other costs: Camera :about £400 to £1000 https://www.edmundoptics.eu/f/point-gre ... ras/15023/

HEQ5Pro: about £1000 (https://www.rothervalleyoptics.co.uk/sk ... ripod.html)
Total for: Lunt LS50THa+camera+mount= £2829 (assume £500 for camera) - not including computer and other small accessories

Total for modified scope= £2829 + another £ 1478

Approximate cost of 90mm modified scope = £4307

Is that about right ?
I did not properly understand all the parts from around the OTA focuser onwards. I assume it is possible given the right expertise and purchase of all the right parts, as the Great Attractor's modified scope gives incredible images, probably among the best high resolution pictures of the sun's surface I have seen on this site or anywhere in fact. Maybe Great Attractor could clarify my uncertainty over the components from the back of the 90mm scope (a listing of the components all that is necessary) in their sequence. Am I about correct about the costs, or is there a less expensive way to go ? second hand or a special solar telescope business I don't know about.

Thanks.
Magnus
London


Solar: H-alpha": Quark Chromosphere filter; Baader white light filters
Scopes: Altair Astro Travel ED70mm (F 420mm, D=70mm);; Skywatcher 90mm (F 910mm D=90mm); GSO focuser;;Altair Astro 60mm guidescope (D=60mm,F=225mm)
Cameras: ASI120mm-S,ASI174mm
Mount: SW HEQ5 Pro, SW EQ3 Pro Synscan (SW = Skywatcher),Vixen Polarie tracker (portable setup)
Accessory: SW Auto-focuser
User avatar
GreatAttractor
Almost There...
Almost There...
Posts: 964
Joined: Sat Jun 01, 2013 1:04 pm
Location: Switzerland
Has thanked: 747 times
Been thanked: 753 times

Re: Questions about 90mm mod to Lunt LS50THa by Great Attractor

Post by GreatAttractor »

Hi Magnus,

The mod's purpose it to increase resolution; contrast is about the same (i.e., not too high when observing surface details visually, but the prominences are excellent. On camera, contrast is of no issue, one can always record with lower gamma and/or enhance contrast in post-processing.)

The prices seem right, though it was noticeably cheaper back in the day (I bought the D-ERF in 2013, the mount in 2014, the Lunt in 2015, and the BF15 I got cheaply from Solarchat's classifieds).

Maybe let's continue the technical discussion in the mod's thread.
the Great Attractor's modified scope gives incredible images, probably among the best high resolution pictures of the sun's surface I have seen on this site or anywhere in fact
I'm glad you like them, but objectively my scope cannot compete with others' 5", 6", 8", 11" and 14" setups ;)


My software:
Stackistry — an open-source cross-platform image stacker
ImPPG — stack post-processing and animation alignment
My images

SW Mak-Cass 127, ATM Hα scopes (90 mm, 200 mm), Lunt LS50THa, ATM SSM, ATM Newt 300/1500 mm, PGR Chameleon 3 mono (ICX445)
Post Reply