Wide FOV w/Lodestar

[HiloDon]

Hi All,

I have been wanting to get a wide field of view with the Lodestar to view larger nebulae, but the relatively small sensor makes it tough. I saw that Nytecam tested his focal reducer to increase FOV, so I thought I would try it on my 80mm refractor. The problem using the 2" F6.3 or 3.3 is that you can't get sufficient in travel to focus. But, the 1.25" design of the Lodestar allows a 1.25" .5x screw on FR to be moved forward inside the draw tube. So, last night I tried my cheapo .5x with my 80mm f7 Barska refractor. I used a one inch nosepiece and a 10mm extension to set the spacing. I actually measured the FOV by timing a star on the Celestial equator with tracking off. The resultant horizontal FOV was 1.5 degrees. That gives a focal reduction of about .31 and a resultant focal length of about 250mm with my Barska 80mm. I also used my narrowband Ha filter mainly to cut down on the star bloat. Here are some results. I was pleased with the FOV, but there is noticeable coma in the corners. If there is any vignetting, it isn't too bad. I was wondering if the coma could be reduced or eliminated with a better quality FR. I think this is a GSO model. Does anyone have experience with other 1.25" .5x reducers? I would appreciate any comments or suggestions.

Thanks,

Don

[AstroEd]

I plan to try my MFR-5 x2 on my 80mm and Lodestar X2 color soon as the gear arrives and weather permits. My first set up will be native FOV but my 2nd will use the FR I will post the results of both in my thread I started about the new equipment

[AstroEd]

By the way I forgot to say those are some great shots once you figure out the coma issue you will amaze us further. I am sorry that I am too new to this hobby to offer advise I can not figure out FR focal lengths and such I just plug it all in and fiddle till I can focus proper and go. I am getting some parfocal rings though so once I find the optimal focus position for my setups I can use them to repeat the results.

[HiloDon]

Thanks, Ed. I'll be interested to see your results with the MFR-5. It is expensive, but maybe it's worth it. I think it can get you to a .33 reduction. BTW, I''m going to make another post here to clarify an error I made on the focal reduction I had.

Don

[HiloDon]

Hi All,

I want to correct something I stated in my original post. The focal reduction I had with the stated spacing was about .45, bringing the focal length down to about 250mm. The focal ratio for the 80mm scope would be about 3.1. Hope that makes sense.

Sorry for the error. Too many ratios to think about.

Don

[Paul81]

I really like the wide field of views - I was looking at a set of adapters to use camera lenses a little while ago to get similar focal lengths. Must go-ahead and purchase sometime. The Ha filter continues to prove to be a really excellent addition for video astronomy.

I have a similar 0.5x reducer in use on the 6" RC. It does seem to work very well, maybe a little coma. My main 'complaint' is that it makes the focal sweet-spot really small, so focus has to be spot on and cooling of the metal tube can shift focus enough to need a tweak. No big problem though and gives me a focal length (and F-ratio of F4.5) that is reasonable for the majority of DSOs. I have a Astro-physics CCDT67 to try at some point too - but need a load of adapters / spacers from 2" threads to C-mount.

Maybe santa will bring me a nice 80mm 'frac for Xmas, oh and a Ha filter and a filter wheel with RGB filters would be nice too... Hmmm...

[HiloDon]

Hi Paul,

Thanks for the idea on using camera lenses to get a wider FOV. I have a Nikon lens to c mount adapter that I used for my video finder system. After I read your post, I tried it with the Lodestar and my old Nikon 200mm lens. It was daylight, but with aperture stopped down I was able to get it focused, so it should work. I just need to figure out a way to mount the Ha filter. I found a female c-mount to t adapter that should do the trick. I also have an old Nikon 105mm lens I'll try as well. If I get anything decent, I'll post it here. There are a number of large nebulae I would still like to get.

Hope Santa delivers on your Xmas wish list. Let's hope he follows SGL.

Don

[arkosg]

Hi Don,

I tried out some SLR lenses with my Mallincam Jr. Pro/PC, and I was (generally) able to get most of them to work, though focus was annoying (depending on the style of focus/zoom).  They do give you a wide field,  but the aperture is small.  Mounting the Mallincam on a tripod worked because of the rectangular body/mounting holes, but that wouldn't work with the Lodestar, so I'm guessing you'd need rings (?), which hopefully wouldn't complicate focusing.

Let us know if it works out....

- Greg A

[arkosg]

Ooops, forgot to add one comment - there are inexpensive photographic step down adapters that would allow you to add a filter to a standard SLR lens; I have a couple of Fotodiox ones I got "just in case" so I can try my 2" filters with the lenses and the Mallincam/Lodestar (when I finally get around to it!) which seem to work fine.

Cheers,

- Greg A

[HiloDon]

Thanks, Greg. I figured out a way to mount the 1.25" filter. I took out the lens of one of my 1.25" color filters that I never use and can mount the empty ring inside the Nikon to c-mount adapter with adhesive. I'm going to make some rings out of ABS tubing to mount the whole setup on top of my 80mm refractor. The rings will be at the front barrel and center hand grip ring, so I will be able to focus and use the aperture ring. I need to buy some stuff at Home Depot tomorrow to get it all done. I'll post some pics of the final setup and hopefully some results if the weather cooperates.

Don

[HiloDon]

Hi All,

I figured out a way to get an even wider FOV than I had with the focal reducer and my 80mm refractor. I modified one of my finder scopes to accept the Lodestar. I simply unscrewed the eyepiece and pressed in a 2" to 1.25" barrel adapter. A few wraps of electrical tape made it fit perfectly. The finder has a focal length of about 180mm which should give a horizontal FOV of about 2.1 degrees with the Lodestar. Last night was cloudy and rainy, but I was patient and got a few brief openings. Attached are captures of the California Nebula, the Flaming Star Nebula and the Rosette Nebula. I wanted to get the Horsehead and Flame but the clouds wouldn't cooperate. There is still a bit of coma apparent. I figure the optics aren't the best, but for near real time observing of large nebulae, this method has some promise. And, it's cheap. Let me know what you think. My next attempt will to try pushing the focal reducer with my 80mm ST. I think I can get it down to a FL of 150mm.

These were all taken with the NB Ha filter. I would like to try some color with a Baader UV/IR cut filter to reduce the star bloat. I'll post here if I get anything decent.

Thanks,

Don

[Paul81]

There is nothing good old electric / gaffer tape can't solve! Nice work Don, those shots have came out superbly!

You have me thinking about taking my finder apart now..

Sent from my iPhone using Tapatalk

[Martin Meredith]

The images are surprisingly good. This sort of approach could also form the basis for a grab and go given a lightweight tracking mount…. not that you necessarily need to go anywhere with your skies 

Martin

[shirva]

Nice work Don. .Great images..davy

[HiloDon]

I was surprised, too, Martin. I think the Ha filter helps. I want to try some color shots, but I'm not expecting much.

Thanks, Paul and Davy.

Don

[Spacedout]

Wow, now that is a finder scope, very nice  Do you have a way to broadcast these views Don? 

Thanks 

Karl

[HiloDon]

Hi Karl,

I have thought about broadcasting, especially when I'm having a great night and would like to share what I'm seeing. I use a Mac exclusively, so what do I need to get on line? Is the time zone I'm in present a problem? It would be nice if you could DVR a session so people could view it when they want and speed through the dull parts. I guess it wouldn't be live, but you could still watch it live if you want.

And, thanks for the feedback. I was out again last night and saw some more. The Heart and Soul, Orion (never saw it like that), and Wide field HH and Flame. I was going to stay up and get Eta Carina that is visible here, but clouds rolled in and I called it a night. I'll post some captures later.

Don

[arkosg]

Hi Don,

Nice work (as usual!).

I was looking at your photo of your finder with the Lodestar attached... and went and looked at my Celestron finder.

I was able to unscrew the narrow eyepiece portion, but the hole it leaves is not big enough to press much of anything 

in there... did you take off the whole back "cap" (it seems glued on with mine) and then replace it with a 2" to 1.25"?

Can you post a few more shots?

Cheers,

- Greg

[Spacedout]

Hi Don,

You are welcome they are great images and credit where credit is due! 

Yes you can broadcast and I wish more would take that side of things up it's fantastic!  As for live, unless it is the Moon or Planets no one is actually live, just near live.  The fastest I can get in good conditions is 2 seconds on really bright things like M42 but for most DSO you're talking 7 seconds to 56 seconds and others who have better telescopes up to 3 minutes!  Besides in my opinion, if someone is broadcasting even if it is just a tutorial it's live!  As for the DVR, I can record all my broadcasts from start to finish using my encoder X Split but I doubt anyone would want to see that in full so I generally take snippets of the best bits.  As for your time zone not a problem, viewers tend to visit from all over just like here and the more times zones we have the better.  I know if I could see Hawaiian skies live I'd watch for sure!!

Anyway if you (or anyone else on here for that matter) would like to know more then let me know I'd be delighted to help get you set up!

Look forward to your' latest catch too!

Best wishes

Karl

[HiloDon]

Hi Don,

Nice work (as usual!).

I was looking at your photo of your finder with the Lodestar attached... and went and looked at my Celestron finder.

I was able to unscrew the narrow eyepiece portion, but the hole it leaves is not big enough to press much of anything 

in there... did you take off the whole back "cap" (it seems glued on with mine) and then replace it with a 2" to 1.25"?

Can you post a few more shots?

Cheers,

- Greg

Thanks, Greg. I unscrewed the whole back cap. On my ES, the eyepiece and back cap are one piece. My Meade finder has the eyepiece separate, but the back cap is screwed in. The tube size is just slightly over two inches. That's why I did a few wraps of electrical tape on the adapter.

Don

[HiloDon]

Here's a few more "finder" captures I got last night.

Paul's Lodestar Live program is a dream to use. Once I set the exposure, I sum stack and just watch as the image gets brighter and brighter. It's amazing to see these objects appear on the screen, especially the ones I haven't seen before. Can't wait to get North America and Eta Carina.

Don

[Martin Meredith]

Don, that's an incredible shot of the Horsehead with a finderscope! Not to mention the details in the Heart & Soul. I think you're on to a winner!

Martin

[arkosg]

Thanks Don!

I will take another look and see if perhaps the back cap on my Celestron finder is, in fact, screwed in place as are yours.

Fantastic wide field shots, BTW, especially with a finder!

Cheers,

- Greg A

[arkosg]

Don,

You were absolutely right - with a bit of initial effort, the back cap did just screw off my Celestron 9x50 finder as well.  The threads 

appear to be SCT or 2" threads - I was able to use a SCT m/m ring, together with an SCT-to-T adapter to connect the Lodestar 

directly to the finder (spacing TBD, but I have T spacers if needed).  No tape required!  ; - )  Thanks for thinking this up, Don!

How fiddly was getting the Lodestar to focus?  That's the only fly in the ointment with using threaded connections....

- Greg A

[HiloDon]

Thanks, for the feedback, everyone. Greg, the focusing was very simple. I did a coarse focus by moving the lodestar in and out in the holder. I tighten it. I have a compression ring holder which I think helps keep the Lodestar square and centered. Then I use the front objective focus adjustment to get the fine focus and lock it down with the locking ring. Most of these finders have that, but not sure about your Celestron. You will have some problems with focus if you have a fixed connection to your T ring. If you have a male SCT, why not just use a 1.25" visual back? Then you can slide the Lodestar in and have means to use 1.25" filters. The other nice thing about this setup is that once you have it focused, it stays that way and unless you remove the camera, you can use it again the next night if you want to do the same type of viewing.

Let us know how your setup works out and post some results.

Don