Barlow with Nikon D7200

[pshepp1890]

Hi all,

I have a Nikon D7200 and recently bought a baader 2.25x Hyperion Barlow and all the nessacery adaptors. I just can't get clear pictures with it. 

What distance should the Barlow lens be from the dslr chip? Is it 55mm just like a coma corrector?

Thanks everyone. 

Edited October 19, 2016 by pshepp1890
Add info

[Steve Ward]

Should make no difference to focus as such other than the focus point will be further out.

If you have removed a diagonal in order to attach the camera in a straight line then you will need an extension tube ( 50mm or so ) to take up the 'missing length' of the light-path through the diagonal that is no longer there.

The distance between the Barlow lens and the chip just determines the magnification it produces , if you were to put a 2" extension tube between the Barlow and camera the 2.25x would increase to nearer 3x , unscrew the lens element and attach it direct to the camera adapter and it would drop to around 1.6x.

[Thalestris24]

Hi

Remember that the Barlow will more than double your focal length and do the same to your focal ratio... What targets are you using it for - Moon? What scope are you attaching it to?

Louise

[pshepp1890]

Mainly the moon. Maybe some DSO's. my scope is a skywatcher 150pds.

cheers both. 

[Lonestar70]

55 minutes ago, pshepp1890 said:

Mainly the moon. Maybe some DSO's. my scope is a skywatcher 150pds.

cheers both. 

Are you trying to use the Barlow in conjunction with the SW Coma corrector?... if so then remove the Coma Corrector since this will be forcing a 55mm back focus limit which, of course, cannot be attained with the length of the Barlow and T-adaptor etc. attached.

This particular Barlow has been designed to produce a true flat field so a Coma Corrector should not really be necessary.

Are you using the Live View function with a PC/Laptop for focusing or are you using the rear view screen?

 

Edited October 20, 2016 by Lonestar70

[pshepp1890]

6 hours ago, Lonestar70 said:

Are you trying to use the Barlow in conjunction with the SW Coma corrector?... if so then remove the Coma Corrector since this will be forcing a 55mm back focus limit which, of course, cannot be attained with the length of the Barlow and T-adaptor etc. attached.

This particular Barlow has been designed to produce a true flat field so a Coma Corrector should not really be necessary.

Are you using the Live View function with a PC/Laptop for focusing or are you using the rear view screen?

 

Hi,

I'm not using a coma corrector with the Barlow. Just dslr / adaptor / Barlow. I use backyard eos. When I take photos, they are black. Even when I go extreme 12600iso 10 min just to simply see something, I get nothing but black screen. 

[Alien 13]

2 minutes ago, pshepp1890 said:

Hi,

I'm not using a coma corrector with the Barlow. Just dslr / adaptor / Barlow. I use backyard eos. When I take photos, they are black. Even when I go extreme 12600iso 10 min just to simply see something, I get nothing but black screen. 

Have you tried this set up in the day time on a distant TV Ariel or similar to make sure focus is possible without extra extensions etc? The other thing is that stars wont show until focus is close to perfect.

Alan

[Lonestar70]

2 hours ago, pshepp1890 said:

Hi,

I'm not using a coma corrector with the Barlow. Just dslr / adaptor / Barlow. I use backyard eos. When I take photos, they are black. Even when I go extreme 12600iso 10 min just to simply see something, I get nothing but black screen. 

Hi,

Ok then it was just a thought.

You say above that you are using Backyard EOS... But I assume you meant Backyard Nikon... BY-EOS won't work properly with a Nikon... also are you using the latest V2.01 release? earlier versions may not fully support the D7200.

It sounds like your shutter is not remaining open for the required period.

I assume you have set the camera to full manual operation and set it for BULB mode.

I would suggest also that you don't use in camera dark subtraction so make sure that is switched off in you camera menu's.

Are you triggering the shutter using BYN's intervalometer via the usb connection? and have you set BYN's shutter control selection panel for this correctly? (you need to select the type of release cable)

Or are you using a separate external release?

Have you told BYN to save to PC? and also what type of exposures you want to take/save (RAW, JPG, BOTH) I would suggest you use RAW for best results in stacking.

Have you told it where to store the pictures? i.e have you set up a folder and told BYN where it is?

BYN has a preview function which should show the last picture taken regardless of where it is stored... have you tried this.

I would agree with Alan regarding trying it during the day on a distant object (at least a mile away or more) to find your focus point, the 150pds focuser is quite sensitive, even with the 10:1 knob, and it is easy to go past the correct point and the Barlow will make this even more tricky... and you may well need to use an extra extension with a x2.5 Barlow since this will place the focus point a good way out and the 150PDS focuser may not have sufficient outward travel.

Once you have found the right point make a suitable mark on your focuser draw tube so that you can more easily find it later.

Then set up BYN and take some short daylight subs and make sure you can see them... and store them.

Once that is sorted you can then set up for Manual long exposures knowing that BYN will at least be saving them... and you will have a pretty good start point on your focus location... after that it is a matter of getting used to fine focusing using the live view focusing capabilities in BYN.

I hope this helps a bit.

I use BYN with my Nikon D90 on my 150PDS.

Best regards.

Sandy.

 

Edited October 20, 2016 by Lonestar70
added extra text to the daytime testing section.

[pshepp1890]

Hi thank you so much for your reply! I've been so busy I've not had a chance to get back to it. 

I meant to say backyard Nikon yes lol my mistake. 

Im using the backyard to control the shutters of the camera and it seems to be working fine as I've used it to take images without a Barlow and it takes them seamlessly. 

Its just when I add the Barlow is when everything is black.

it has to be a focus issue / back focus as everything else is perfect. Just as soon as I add the Barlow.

cheers everyone. 

 

[mikeyj1]

Hi,  I had a focus issue with my D5300 on the 150pds and changed adaptors to suit.  The idea of setting up in the day is a good one, more light and you can see if you are getting closer to focus or not when turning the focus knob.  I dont have that scope any more, but if I remember correctly, I had to come back out from the OTA by about 50mm to get focus with a 2x barlow.

Mike