Barlow or EP Projection?

[Moses_C]

Hi,

I would like to know which method will give the best result, when used with dslr, like 550D.

Let's say both are of good quality ones, like powermate 5x or baader hyperion 3.5mm...which will likely give better quality?

Tq for explanation.

[Cornelius Varley]

What telescope will you be using?

Peter

[skybadger]

If you are doing epp from a 3mm lens you are missing the benefit. IMO, the key benefit is that with eyepieces you can use a longer focus ep with better colour control than a shorter one. With abarlow,unless you play with spacers, the image size is.more of a gaff to control. Theother view is that with a Barlow you have less glass surfaces in thee way.

I use both methods, ep normally to get a f/40 planet image using a 20mm eyepiece.

Mike.

[Macavity]

I must experiment more with eyepiece projection. Especially in cold temperatures, after initially centering (e.g. Mars) in the field, something usually "sticks" (mostly brass retaining rings!) and I jerk the whole telescope setup.

Hyperions are ideal for the task though! With a simple [webcam] nosepiece (shortest extension), the 24mm gives about the same image scale as with prime-focus. With long eye relief you can usually see if the planet is still centred too!

Of course, with shorter focal length Hypes, greater extensions, access to stupendous (unfeasibly large? LOL), f-numbers is rather easy. I was casually wondering about the relative merits of short focal length versus longer extensions though... so thanks.

[Moses_C]

Thank you all very VERY much for all help and explanation.

Btw, i'm just using the C5...you know the spotter?

I plan to maybe just get only one Hyper...only one...for extreme magnification thru EP projection and that's it. Main usage will be for earth bound imaging....not so much of outer space (someday maybe :-) )

Now, is it good to get the 3.5mm or 5mm or maybe 8mm? I dont want to get a long focal length one as that just defeats my intended purpose...

Yes, i know there will be fuzziness and maybe great lost of brightness..but will the 5x barlow out do the Hyperion in this extreme case? If so, then i will go for the 5x...if not, i will just stay with the hyper.

Lastly, has anyone used the 3.5mm before? Is any good for EP projection or is just a useless EP, if compared to the 8mm? Any feedback will be good.

TQ very much again.

[Cornelius Varley]

I think an 8mm would be too much for eyepiece projection, the 3.5mm even more. Before you buy your eyepiece you may want to play will this spreadsheet. Enter your telescope and eyepiece specification in the yellow boxes, you can leave the camera sensor to flange distance at 45mm as this is the same for all DSLRs I think. There are boxes to enter any length of extension tube and barlow lens you might want to use (leave the barow number as 1 for no barlow) and then read the numbers in the green boxes.

Peter

eyepiece projection.xls

[Cornelius Varley]

That should have read leave the barlow number as 1.

Using an extension tube increases the effective magnification of the eyepiece.

Peter

[Moses_C]

I think an 8mm would be too much for eyepiece projection, the 3.5mm even more. Before you buy your eyepiece you may want to play will this spreadsheet. Enter your telescope and eyepiece specification in the yellow boxes, you can leave the camera sensor to flange distance at 45mm as this is the same for all DSLRs I think. There are boxes to enter any length of extension tube and barlow lens you might want to use (leave the barow number as 1 for no barlow) and then read the numbers in the green boxes.

Peter

Hi Cornelius,

Thanks for the cool spreadsheet...its very useful I understand the top part. However, i dont know how to read the magnification, meaning of the term PFR, and the moon part...i'm still at the basics.

What i know is the focal length of scope divide EP, you get the magnification...but this one is different..

One last question, and hopefully i dont have to ask again ... will the image of the 3.5mm, 5mm and 8mm have equally good resolution and brightness? Did baader made them to produce same kind of result, as i see the barrel and size of their EP all look alike...and if i still go ahead with this "crazy idea" of the "greatest" magnification possible but still more or "very very" less able to make out the detail...what would you personally suggest - that is, the 3.5, 5, 8mm or a good 5x barlow? OK, also what would it be like let say i stretch it with the 8mm plus the 10x (100% crop) digital zoom...will the 550D be able to make at least some detail?

I would appreciate your suggestion, cause as i mentioned else where in the forum, i wont get the chance to test it out in the place i live...once purchased, that's it...no returning nor refund for me.

Oh oh oh...one final of the final question (sorry), will the image of a webcam (cheap ones like the philips) be better than the 10x digital zoom of the 550D, or almost the same pixel DSLR? What i mean is, comparing the magnification and live video quality of webcam and the maximum digital zoom of 550D (or similar DSLR), which will be better? Cause i'm really interested in just extreme blowing up...not wide angle photo or video..i hope you grasp my "crazy" intention.

Thank you, thank you, and thank you again!

[Macavity]

Interesting FACTOID I picked up, reading around on the subject. If you're eyepiece projecting, you should really use a lower power eyepiece with a larger (post eye-lens) extension. In "normal" use rays emerge from the eyepiece parallel. When you're "projecting" they have to converge onto the camera chip. All about minimising spherical aberration, apparently.

As a matter of personal experience the errors on "predicting" the image scale tend to be large. It's difficult (a bit fraught) to measure the precise distance from camera chips to eye lenses - And you never really know the "node point" of the eyepiece. To some extent, down to trial and error. Once you've decided on the eyepiece / extension - A DAYLIGHT "experiment" is perhaps easiest? Or so I've found...

[Cornelius Varley]

You can find a useful astro exposure calculator here. The program has a section to calculatio effective focal ratios and exposure timers using eyepiece projection. A 3.5mm eyepiece would give an impractical f number of about f111 with no extra extension tubes. Basically the image would be very dark and a very small field of view. Even an 8mm eyepiece would be too small to give satisfactory results. Eyepieces used for eyepiece projection tend to be be around 20mm in focal length to give a reasonable image scale and exposure times.

I'll rewrite the spreadsheet later to add some extra info.

Peter

[Cornelius Varley]

Whoops. I appear to have turned red.

Peter

[Mr Moff]

I've also been looking at attaching my DSLR to Hyperion ep's or barlows.

I was looking at the Hyperion zoom Barlow. It says it goes up to x6 so sounds like its quite versatile.

Has anyone tried eyepiece projection with one?

Danny.

[Macavity]

Whoops. I appear to have turned red.

Useful calculator / discussion though. Though perhaps not the best of the (Hyperion) breed, I tend to use the 24mm as a starting point. It's lighter and smaller than the others! I'd guess a 40mm extension might yield useful scales for planetary imaging? Handy to have that screw thread for extensions / adaptors to webcams... DSLRs though.

http://www.alpineastro.com/Eyepieces_Accessories/Images/Color%20manual_Hyperion6pager[1].pdf

[Cornelius Varley]

Heres the new version of the spreadsheet.

Peter

eyepiece projection rev2.xls

[Moses_C]

Ok, thank you all for much help.. :-) Good work on the spread sheet.

I found a page just quite sometime ago...it says that the 3.5mm Hyperion is no longer in production because its performance is inferior to the 5mm and 8mm, and you can achieve the same or more focal length with the fine tuning rings, and the image quality would be better..sth like that. I cant remember the link...its from a review site i think.

If in that case, should i then go for the 5mm or 8mm, is there any of you who owns this two and knows which is better for EP projection with the rings? Also, if i use a longer focal length EP, let say 24mm, then put in barlow or those extension rings to magnify the image, will it be better or worse than just using a 5 or 8mm EP?

tq,

[Macavity]

To be frank, as a start, I would use a setup fairly precisely following the one(s) illustrated at the bottom left of page 2 on the above link (repeated here):

http://www.alpineastro.com/Eyepieces_Accessories/Images/Color%20manual_Hyperion6pager[1].pdf

If you're using a webcam the leftmost diagram. If your using a DSLR, the second diagram in from the left. THE whole POINT (I believe) is to use an eyepiece of *modest* (longer!) focal length: 17mm is probably a good start, 24mm too. Use a longer 40mm T2 extension *behind* the eye lens to increase image scale, NOT a shorter (8, 5, 3.5mm) focal length eyepiece.

Hyperions of 8mm or less (I know from personal experiment) rapidly give you *huge* "magnifications" of 7x, 8x, 9x plus, with only small post-eye lens extensions. These are normally too much, even for eyepiece projection, even with short focal length telescopes.

Buy the components (thread converters, T-2 extensions etc.) illustrated on the diagram, and you won't go far wrong. UK suppliers of less-common Baader adapters exist. But e.g. Telescope Service (DE) carry most of these, and offer a sub-one week turnaround on (fellow Germanic) kit.

[Staraddict]

Sorry to revive an old thread... I have a Skywatcher Heritage 5", two eyepieces (25mm and 10mm, although I will soon buy a 7.5" one) and a 2X Barlow lens.

I can view fine with the Barlow lens, but the photos (afocal with a point-and-shoot camera) don't really reflect what I see and are out of focus. Without the Barlow they are fine (well, not perfect, but they can be improved in Photoshop and in particular the moon is really nice). Planets always look small without the Barlow lens.

I saw some photos on the net taken with eyepiece projection which were spectacular, and even with an equipment similar to mine...

So I was thinking... Should I buy a camera projection eyepiece? Should I give it a go or should I experiment a bit more with the Barlow? Maybe take a short movie? It looks like many people stack frames of movies to obtain good results. I have just ordered a camera adapter bracket last week because I can't take movies by just holding the camera....

Thanks for your advice!

[happy-kat]

I guess the out of focus issue when taking images afcoal is camera shake so perhaps your camera braket will resolve that from happening. Afocal should take what ever you eye would otherwise have seen as the eyepeice is doing all the work. Camera afocal normally would be focus to infinity though one of my cameras only does afocal if set to macro.

[Staraddict]

Thanks, I hope so. I just got the camera bracket this morning, but could not test it properly yet because it is not night yet. However, it did fine center on the eyepiece, so I hope it will be OK.