T2 360 rotator, any users or suggestions?

[Space_Plane]

Hi all,

I'm just starting down the path of imaging with a cooled zwo 178mc, and have hit a few bumps! ?

I purchased a geoptik canon-ccd adapter as I'm planning to use it with short focal lenses for now.

Any ideas how best to align the sensor..."squarely" to the adapter, for easier framing etc?  Maybe its not as big an issue as I assume?

I've seen the following T2 rotation adapter which I think I'd just about have the space for.

Anyone ever used them or know if they work ok etc?

Any advice & suggestions welcome ?

[RichLD]

I have used this very combo and it works very well - you will have back focus to spare as it only adds 5.5mm.

I prefer to have my chip orthogonal to the RA and Dec axes as I find it makes it easier to plan framing and mosaics.  

I've now sold my Geoptik adapter and have the very rotator pictured in very good condition for sale. If you're interested drop me a PM ?

Rich

[ollypenrice]

It's easy to align along RA and Dec. Just take a (say) 5 second sub while slewing slowly in just one axis. You'll get a star trails. Are they horizontal/vertical? Repeat after making a camera rotation till they are. I always image orthogonally to RA and Dec. If it means doing a mosaic I'd rather do that because, in the long run, it's easier and more reliable.

Olly

[tooth_dr]

2 minutes ago, ollypenrice said:

It's easy to align along RA and Dec. Just take a (say) 5 second sub while slewing slowly in just one axis. You'll get a star trails. Are they horizontal/vertical? Repeat after making a camera rotation till they are. I always image orthogonally to RA and Dec. If it means doing a mosaic I'd rather do that because, in the long run, it's easier and more reliable.

Olly

I keep meaning to do this 

[ollypenrice]

21 minutes ago, tooth_dr said:

I keep meaning to do this 

Do it sooner rather than later because, as you gain both data and experience, you'll want to add new data to old and if it's at 45 degrees you'll be seriously 'removed word' of!!!

Olly

[don4l]

5 hours ago, ollypenrice said:

It's easy to align along RA and Dec. Just take a (say) 5 second sub while slewing slowly in just one axis. You'll get a star trails. Are they horizontal/vertical? Repeat after making a camera rotation till they are. I always image orthogonally to RA and Dec. If it means doing a mosaic I'd rather do that because, in the long run, it's easier and more reliable.

Olly

Does this still apply if you always platesolve as part of framing the target?

[ollypenrice]

7 hours ago, don4l said:

Does this still apply if you always platesolve as part of framing the target?

Yes, if you're talking about returning to an object at some point in the future. Unless you have a computerized camera rotator (which a few do but most don't) you'll have to replicate the precise camera angle by hand and by eye. This is a terrible job and takes ages. Plate solving can only put the middle of a rotated camera's chip into the middle of the previous image. It can't rotate the camera.

Olly

[RichLD]

To add to my previous post, I use the SGP Framing and Mosaic wizard and Platesolve2. It really is a joy to be able to enter an accurate rotation figure and see exactly what you're going to get. It also makes multi-session imaging and mosaics a breeze! I'm either at 270/90 (long side of chip parallel to the dovetail) or 360/0 degrees. Once I've used the star trail/slewing technique mentioned by Olly I'll do a quick platesolve to be sure I'm dead on.

[don4l]

7 hours ago, ollypenrice said:

Yes, if you're talking about returning to an object at some point in the future. Unless you have a computerized camera rotator (which a few do but most don't) you'll have to replicate the precise camera angle by hand and by eye. This is a terrible job and takes ages. Plate solving can only put the middle of a rotated camera's chip into the middle of the previous image. It can't rotate the camera.

Olly

I use Elbrus to platesolve and it also gives me the image angle - which precisely matches the angles in Cartes Du Ciel.  Rotating to any random angle is all the same.  However, Elbrus is not everybody's cup of tea, and I can see that your method would be very fast, and very reliable.

 

[Space_Plane]

Hi everyone,

Thanks very much for your info & associated discussion, and Rich for your offer.  I'll have to read more into your suggestion Olly, i've never tried it.  I wonder if i can make it work on my star adventurer ?

I haven't quite decided what i'll do just yet, have to think about my spacing a little.

The spec of the geoptik says 19mm, the backfocus of the 178 is 17.5mm and the potential adapter above is 5.5mm, for a total of 42 of I believe the required 44mm? Not sure how to best deal with 2mm!

I'll be using vintage lenses for now, but I think the m42 -> canon adapter I have will work ok here, seems to reach infinity fairly well on my canon dslr.

Supposedly clear spells here over the weekend, might get a chance to start experimenting ? ⭐

Thanks again

Chris

[RichLD]

10 hours ago, Space_Plane said:

Not sure how to best deal with 2mm

You'll be fine given the size of the chip, just focus under infinity on the lens.

[Space_Plane]

On 15/11/2018 at 07:48, RichLD said:

You'll be fine given the size of the chip, just focus under infinity on the lens.

Hi Rich,

That isn't something i've come across before, i'm fascinated.  I've only used these lenses with a DSLR before, and it was really picky about focus / infinity.  The slightest movement knocked it off.  Due in part to larger sensor then i presume?

I managed to get out the other day and experiment a bit, and with the adapters I have, was about 41.5 out of 44mm.  The lens would vaguely focus about half way around the focus ring, but it wasn't great.  I wasn't expecting ~2.5mm to make such a difference to the focus.  Look forward to getting different extensions and trying to get it sorted a bit better.

Cheers

[RichLD]

2 minutes ago, Space_Plane said:

Hi Rich,

That isn't something i've come across before, i'm fascinated.  I've only used these lenses with a DSLR before, and it was really picky about focus / infinity.  The slightest movement knocked it off.  Due in part to larger sensor then i presume?

I managed to get out the other day and experiment a bit, and with the adapters I have, was about 41.5 out of 44mm.  The lens would vaguely focus about half way around the focus ring, but it wasn't great.  I wasn't expecting ~2.5mm to make such a difference to the focus.  Look forward to getting different extensions and trying to get it sorted a bit better.

Cheers

I use a variety of focal length camera lenses - 55mm (Super Multi Coated Takumar) 135mm (Jupiter 37A) and 180mm (Nikkor ED180) all manual focus with a Canon adapter. Because I'm a bit short in terms of flange to focal plane distance, I tend to find that infinity focus tends to be around 2/3rds of the focus travel.

I have always had very sharp focus with all the lenses at this 'virtual' infinity mark on a 4/3 sensor (like the KAF8300). It may be worth mentioning that all of these lenses focus externally i.e. the lens changes in physical length when focussed. I wonder if IF lenses react differently to incorrect register distance?

[jjosefsen]

On 14/11/2018 at 18:02, don4l said:

I use Elbrus to platesolve and it also gives me the image angle - which precisely matches the angles in Cartes Du Ciel.  Rotating to any random angle is all the same.  However, Elbrus is not everybody's cup of tea, and I can see that your method would be very fast, and very reliable.

 

The imaging software I use also tells me the rotation of the camera based on platesolve, either PS2 or blind solve.

[Space_Plane]

On ‎20‎/‎11‎/‎2018 at 22:02, RichLD said:

I use a variety of focal length camera lenses - 55mm (Super Multi Coated Takumar) 135mm (Jupiter 37A) and 180mm (Nikkor ED180) all manual focus with a Canon adapter. Because I'm a bit short in terms of flange to focal plane distance, I tend to find that infinity focus tends to be around 2/3rds of the focus travel.

I have always had very sharp focus with all the lenses at this 'virtual' infinity mark on a 4/3 sensor (like the KAF8300). It may be worth mentioning that all of these lenses focus externally i.e. the lens changes in physical length when focussed. I wonder if IF lenses react differently to incorrect register distance?

I am quite intrigued by this, I always just assumed it had to be as close to infinity / spacing as possible, 'virtual' infinity is totally new to me ?

Its similar lenses I have at present, all vintage takumars, 55, 135 & 200.  When I was out briefly a few days ago it was the 135 I tested, and you're right, it looked about as best focus it was going to get between 1/2 and 2/3 of the travel.

It still looked quite soft though, whether that's just how it is, or whether it would be sharper at more accurate spacing / infinity mark I don't know.

Hopefully find out next clear night!

Thanks