Photo lenses with Lodestar for widefield EAA

[Dom543]

I promised earlier to post photos of my setup that attaches the Lodestar to photo lenses and also allows easy swapping of filters.

Here is my setup with the 180mm Nikkor f2.8 ed lens and Lodestar x2c.

I have an assortment of old manual Nikon and Pentax lenses. I like them for their sheer feel that reminds me to an era, when precision craftsmanship enjoyed precedence to cost efficiency. They also make excellent and low cost short focal length refractors. The most used ones are this 180mm Nikkor f2.8 ed and the 135mm SMC Takumar f2.5. They have the right speed and frame many larger nebulas well.

Here are all parts taken apart.

I list the parts from left to right.

1. Tripod attachment ring (from ebay) bolted to a 4" dovetail.

2. Nikon lens to M42 adapter (from ebay).

3. Teleskop Service filter drawer with T2 threads (with drawer halfway pulled out).

4. 15mm T2 spacer.

5. Teleskop Service camera rotator.

6. Teleskop Service 1.25" eyepiece holder with T2 threads.

7. Lodestar x2c with 1.25" parfocalizing ring attached (the yellow plastic ring is just decoration).

The 15mm spacer and the camera rotator are not essential. The round Lodestar can easily be rotated in the ep holder and with a parfocalizing ring it would not get out of focus. But since I had the rotator, I am using it. Also I feel more comfortable with the ep holder gripping the camera in its middle rather than at its end.

For the Pentax lenses I just use a "Pentax M42 lens to Nikon adapter" (from ebay) added to the front of the setup on the photo.

For Nikon lenses the distance from the flange of the lens to the sensor of the camera should be 46.5mm (for Pentax it is 45.5mm and for Canon 44mm). If the sensor is further away than one cannot reach infinity focus. The total length of whatever adapters and filter stuff is between the lens and the camera should add up to less than this distance. (Actually, less than 46.5mm - 12.5mm = 34mm due to the Lodestar's 12.5 mm flange to sensor distance.) I usually push the Lodestar a mm or two closer in. That way infinity focus is reached around the 100 yard mark on the lens.

To use the Lodestar with an SCT I have this same setup. The only chnge is to replace the "Nikon lens to M42 adapter" with a T2 threaded 2" nosepiece. I have a Baader clicklock 2" eyepiece holder as a visual back on my SCT. The 2" nosepiece slips into this.

So this is the setup. Please feel free to ask questions, if I can help with more details.

A separate post will follow at a later time summarizing some of my experiences with the use of this setup for wide field electronically assisted observing.

Clear Skies!

--Dom

[Paul81]

Thanks for sharing Dom. This type of rig is something I want to try and get running for the late summer autumn so your post will greatly help when it comes to knowing which bits to buy!

[amistybleu]

That is a very nice setup, I would like to do something similar with my C8 OTA and am wondering if you know how I could integrate a 1.25" filter drawer in to this setup..............a double t thread drawer doesn't seem to be jumping out at me, not to mention my setup seems to be begging for the more expensive 2" filters. Can I get away with 1.25" filters here?

[Dom543]

Amistybleu,

My TS T-threaded filter drawer could be screwed in anywhere in your setup, where two T-spacers are joined.

I believe that the only US reseller of TS producs is OPT and I believe that this is the drawer that you need http://www.optcorp.com/teleskop-service-1-25-single-filter-drawer-system.html

The image is not exactly this item and the description is not good either. But it is likely the item you need, as TS has only two of these drawer systems: One with 2" filter threads on the housing and the other with T-threads on the housing. You should double check with OPT that the enclosure has one female and one male T-thread on it and that the drawer is for 1.25" filters. It makes sense to also buy additional drawers. The 1.25" drawers are the same and cost the same as the 2" drawers but also include an additional 2" to 1.25" reducer. (At AgenaAstro.com such a reducer alone is $20+.) If you unscrew the reducer, the same drawer can also be used with 2" filters.

A possible alternative is the Orion filter slider system. "http://www.telescope.com/Orion-6-Slot-2-Filter-Slider/p/113381.uts?keyword=filter slider"

or this "http://www.telescope.com/Orion-8-Slot-125-Filter-Slider/p/113380.uts?keyword=filter slider"

I don't have this and have seen it only recently on the Orion website. It seems that it works as an eyepiece extension tube. You put it in the ep holder and put the ep or camera in its other end.

A third alternative is to use a filter wheel. Almost every camera maker also makes filter wheels. But I don't have expeience with any of them. I believe that they are more expensive.

Earlier, when I used light pollution filters and after Christmas, when I got my first H-alpha filter, I used then screwed on the end of the eyepiece. Since I have always had the parfocalizing ring on the camera, it was easy to slide the camera back to the same position after a filter change. I only started to use the filter drawer, when I got into these multi-color experiments.

By the way, focus usually needs to be readjusted after every filter change. The only exception is, if you use filters from the same manufacturer that are guaranteed to be parfocal. Astronomik advertises that all their filters are parfocal. Baader says that filters of the same size are parfocal.

[amistybleu]

Thank you Dom, this is great information..............they sure are proud of those filter drawers / accessories. looks like I could exceed the dollar amount of the rest of my gear in filters........

[arkosg]

Hi there,

Just to add to Dom's excellent info, there is another option for filter sliders.  I use one by Starizona:

http://starizona.com/acb/Starizona-Filter-Slider---Complete-System-P3518C91.aspx

It is very well made, though not cheap (especially if you get extra sliders for all of your filters), but it 

works nicely - and is so much easier for inserting/removing filters than screwing them on the ends 

of eyepieces or nosepieces!  It makes doing "A/B" comparisons easy, which is great for testing how 

well certain filters work or do in different conditions (I'd often not bother, beforehand, simply because 

of the effort of changing between filters).  Now it's (literally) 2 seconds....

Cheers,

- Greg A

[Dom543]

Field of view of photo lenses with Lodestar

I have created an album to illustrate the field of view of photo lenses of various focal length on a number of large winter nebulae. http://stargazerslounge.com/gallery/album/3729-widefield-lodestar/
The purpose is to help to find the focal length that frames a particular object the best on the 1/2" lodestar sensor. For demonstration purposes several different compositions of the same objects are also included.

The images are in the order of increasing fields of view. (For curiosity, please note the that the small red smear at the top center of the last image is the entire object of the first image.)

Here is the list of the 14 currently included images associated with the focal lengths of the lenses.

300mm - Flame and Horsehead Nebulae

200mm - Rosette Nebula
200mm - Jellyfish Nebula
200mm - Monkey Head (aka Tadpoles) Nebula
200mm - Flamunig Star Nebula

180mm - Rosette Nebula

135mm - Rosette Nebula
135mm - Heart Nebula
135mm - Baby (aka Soul) Nebula
135mm - Witch Head Nebula (no filter!)

85mm  - Heart and Baby nebulas in the same field
85mm  - FlamingStar and MonkeyHead nebulas in the same field
85mm  - Seagull Nebula

35mm  - Barnards Loop (with tiny Flame and Horsehead)

Most of these captures are from past January and February and they have been posted previously on various threads here on SGL or on CN. They are, of course, made with a Lodestar x2c and LodesterLive v.0.11.

With one exception all these images were taken with narrowband H-alpha filter. The single exception is the Witch Head nebula, which is a blue reflection nebula and hence would be invisible with an H-alpha filter.

The reason for the inclusion of the Witch Head Nebula image is to demonstrate why narrowband filters are almost a neccesity for widefield near-live images. Large nebulas have low surface brightness and there are many foreground stars in the wide field of view. In order to capture the faint nebulas, we need to take relatively long exposures. But at those exposures the stars get blown out and owerwhelm the nebula that was supposed to be the main object of the image. Narrowband filters take a drastic cut out of the light of the stars and that way prevent them from dominating the image.

Overwhelming foreground stars are not such an issue for galaxies, that are usually small and can be isolated from interfering stars. (The few large galaxies are sufficiently bright so that they don't need such long exposures.) Globular clusters and planetary nebulas are also mostly immune to this issue, as they are not wide field objects either.

There are, of course, also many other interesting issues related tho the use of photo lenses with the Lodestar but we can get to those in separate posts.

Please feel free to make comments, corrections or to ask questions.
Clear Skies!
--Dom

[PeterW]

Monkey head is ngc2174 in Gemini... Go and look at the Sharpless catalogue for inspiration, there are a lot more cool targets where these came from....great shots

Peter

[Dom543]

Thank you Peter!

It looked like a monkey head, I remembered that there was a Monkey Head, so I thought (without checking it) that this was the Monkey Head. Maybe I should change it to Orangutan Head, except that SGL doesn't allow authors to edit their posts. Once the "Post" button is pressed, the content is frozen for eternity.

I bought my Lodestar last September and have only recently started to save my views. This far my main source for potential targets have been a book by Ruben Kier: 100 Best Astrophotography Targets and a CD by Jerry Lodriguss: Asrophotographer's Guide to the Deep Sky. Mostly because they do include images and info on the optics and sensors used. That helps in the composition of images. My objective with posting the shots in my gallery has been similar: To help others to see what objects would fit on the 1/2" sensor of the Lodestar using the various lenses.

Thank you for suggesting the Sharpless catalogue.

Clear Skies!
--Dom

[PeterW]

Night at observers guide, Sharpless catalogue.... With EAA you can go after pretty much anything....

Not come across the ones you mentioned.

Cheers

PeterW

[Dom543]

I found a very nice downloadable pdf atlas of the Sarpless II catalog on this website http://www.reinervogel.net/index_e.html?/Sharpless/Sharpless_e.html.

It also includes images and all data that one would ever wish.

Where I observe, I usually have no or only very weak internet connection. So for me information, that is in form of a book, CD or a file residing on my computer is much better that something "on the cloud".

Clouds are not fiends of astronomers...

--Dom

[PeterW]

Good resource, though it is missing a few. Start big and bright and go from there. You could use any good charts and then explore all the marked objects in a region.

Cheers

Peter

[amistybleu]

Hi there,

Just to add to Dom's excellent info, there is another option for filter sliders.  I use one by Starizona:

http://starizona.com/acb/Starizona-Filter-Slider---Complete-System-P3518C91.aspx

It is very well made, though not cheap (especially if you get extra sliders for all of your filters), but it 

works nicely - and is so much easier for inserting/removing filters than screwing them on the ends 

of eyepieces or nosepieces!  It makes doing "A/B" comparisons easy, which is great for testing how 

well certain filters work or do in different conditions (I'd often not bother, beforehand, simply because 

of the effort of changing between filters).  Now it's (literally) 2 seconds....

Cheers,

- Greg A

Hi Greg, do they have M48 to T-2 as I would be fitting this in between T thread extensions

[arkosg]

Hi Greg, do they have M48 to T-2 as I would be fitting this in between T thread extensions

I don't know if they carry a M48 to T2, but this kind of adapter can be found elsewhere, eg.

http://agenaastro.com/blue-fireball-m48-male-t-t2-male-adapter-t-05.html

http://agenaastro.com/blue-fireball-m48-male-t-t2-female-adapter-t-12.html

I have an M48 to SCT, and M48 to 2" nosepiece, since those are the connections I use.

Cheers,

- Greg

[Dom543]

There was a break on the otherwise solidly cloudy skies of Seattle yesterday. So I set up to try my new SMC Takumar 6x7 105mm f2.4 lens that I have recently bought on ebay from Japan. This is my first medium format lens and I bought it to see, if its unusually generous back focus would open up some new opportunities. In particular, I was thinking of perhaps getting a filter wheel.

Unfortuantely, my first attempt was not encouraging. At its maximal f2.4 this lens needs to be refocused, when switching from H-alpha to OIII filter. This doesn't bode well for a filter wheel...

These old manual lenes are essentially achromats. They don't focus the different colors to the same point. They can be used, and they are used, for narrowband imaging but the focus needs to be adjusted to always focus the particular light that the filter transmits to the plane of the sensor. The faster the lens, the narrower the range of sharp focus. So much so that I, personally, have given up on using any of these lenses at speeds faster than f2.

Some lenses are better than others. E.g. I have successfully used my 85mm f1.8 SMC Takumar for both all-spectrum and multi-spectrum narrowband. But to save frustration, I stop it down to f2.8. It is still very fast optics. Here is an example image of full-spectrum (i.e. no filter) use. http://stargazerslounge.com/gallery/image/27960-85mm-f28-antares-rhoophiuchi-complex/Nice tight round stars up to the edges and sharpness sufficient to split close doubles. I also have captures of the same complex with the use of blue and H-alpha filters with similarly good results. There was no reed to refocus between the filters, even though blue and H-alpha are at the opposite ends of the spectrum. The 85mm f1.8 is somewhat of a cult lens among portrait photographers and has exceptional reputation.

I also had similarly good experience with the Nikkor 180mm and 300mm f2.8 ED lenses with no need for refocusing. But those use low dispersion glass and hence are supposed to have substantially less color. An example is here http://stargazerslounge.com/gallery/image/27962-300mm-f28-eastern-veil-aka-network-nebula-swedish-palette/.

The conclusion of this post is that some old lenses work well with no need of refocusing. Others work for narrowband only and need refocusing after filter changes. Of course, all lenses work fine for single spectrum narrowband, as there is no CA there. It would be nice to have a data bank of lenses that work for astro.

After about 30 minutes the vapor in the air condensed into clouds and my short astronomy session was over. I cannot blame the lens for that...

Clear Skies!

--Dom

[Dom543]

As clouds still dominate the skies in Seattle, I used the evening to add a couple of more recent captures to my "Lodestar Widefield" gallery. Several of the newer images are multi-color narrowband. Information on the filters and exposure times is included in the descriptions.

The primary purpose of the gallery is to illustrate the field of view of the Lodestar in combination with optics of various focal lengths. Captions start with the focal length used. If the gallery is sorted by image captions, then the images line up in the order of their focal lengths, i.e. in reverse of their fields of view. http://stargazerslounge.com/gallery/album/3729-widefield-lodestar/?sort_key=caption&sort_order=desc

Here is a list of the currently included images associated with the focal lengths of the optics in the order of increasing FOV.

1000mm - Dumbbell Nebula

1000mm - Thor's Helmet

.900mm - Trifid Nebula

.900mm - Bode's Galaxy

.400mm - M81 and M82 Galaxies

.300mm - Flame and Horsehead Nebulae

.300mm - Eastern Veil aka Network Nebula

.200mm - Tadpoles Nebula

.200mm - Rosette Nebula

.200mm - Jellyfish Nebula

.200mm - Flaming Star Nebula

.180mm - Rosette Nebula

.180mm - Carina Nebula

.135mm - Witch Head Nebula

.135mm - Rosette Nebula

.135mm - Heart Nebula

.135mm - Baby (aka Soul) Nebula

..85mm - Antares / Rho Ophiuchi Complex

..85mm - Seagull Nebula

..85mm - Heart and Baby nebulas in the same field

..85mm - Flaming Star and Tadpoles nebulas in the same field

..35mm - Barnard's Loop (with tiny Flame and Horsehead)

A few objects have multiple images included to illustrate different spectral mixes or palettes.

Clear Skies!

--Dom

[Dom543]

No-name Nebulettes in Cygnus

Somewhat whimsical byproducts of testing my new Samyang 135mm f2.0 ED lens.



They look like some lucky souls escaping from the violently burning fires of hell.

I am not sure if they are separate nebulas or the dust of a dark nebula carved them away from a large Hydrogen cloud.
By the way, they aren't as small as some might think either. They only look small in the 3 degrees diameter field.

The subtitle of the image says everything: 5x60sec exposures with an H-alpha NB filter mean-stacked.
Lodestar x2c with LodestarLive v.0.12

Sprinkler Head Nebula

Another rarely visited nebula in Cygnus. So much so that it doesn't even have NGC or IC numbers.

 

5x60sec exposures with a 7nm H-alpha filter mean-stacked in LodestarLive v.0.12.

Clear Skies!

--Dom

[Paul81]

Thanks for posting Dom - these are two objects I have never seen before