Advice needed for camera lens focus and using a remote

[Carole]

As you are probably aware I have always struggled to get focus with the camera lens.  I managed to get it reasonable at one time using a Y mask and also on my laptop using a facility in Canon Utility which Julian showed me, but this did rather depend on seeing a land object. 

I am going to southern Spain in June and I want to have a go with my ioptron Skytracker which despite having bought it 18 months ago have not as yet used it due to timing and my DSLR packing up.

So I got it in the garden a couple of nights ago to practice for Spain.  The Skytracker itself seems quite easy to use, and I managed to get around 3.5 minute exposures without trailing but I spent ages trying to get focus without using a laptop and trying to use the remote timer.  The remote timer is hopeless to try to set in the dark, I just cannot see what I am doing.  It might just work if I can do the settings indoors and then go out and plug into the DSLR. 

As regards focus I was totally unable to get any spikes using a Y mask, and the smallest Bahtinov mask (made for my WOZS71) just showed the shapes of the Bahtinov spokes inside the star itself!  Plus trying to see what I was doing on a very tiny LCD screen was very difficult.

I have now made myself a Hartmanns mask (with triangular holes), but yet to try it out. 

I am using a 28 - 200mm zoom lens and will probably be using it at around half zoom. 

Just wondered whether any-one had got any tips both on getting focus and using the fiddly remote.
I don't really want to have to take a notebook with me to Spain, a) I don't own one. b) It will have to go in the suitcase (new UK flight rules), c) Will have to load it all up with the relevant software which was a bit difficult in the first place.  d) No idea how long the battery will last or whether I will have access to power. 

Carole

These are some of the shots I got trying to focus with the Y mask.  A couple of them have spokes, but when I successfully used it previously I was getting a similar pattern to the Bahtinov mask with a spoke through the middle - faint of course.

[MarkS]

I'm finding it impossible to interpret those Y-mask images, sorry.

Mark

[Carole]

I'm finding it impossible to interpret those Y-mask images, sorry.

So was I.

But basically I would like to know how every-one else gets lens focus, especially if you are not using a laptop. 

Carole

[MarkS]

Take a series of test images at very slightly different focus positions, review the images at 10x magnification to choose the best position.  If your lens has no focusing scale then improvise:  http://forum.orpington-astronomy.org.uk/index.php?topic=10030.15

Mark

[Carole]

Thanks Mark, I will see what I can improvise, but I still don't know how to tell when i am actually IN FOCUS. 

I will try with the Hartmann's mask I have made next clear night and see if that might give a clearer indication and also try to mark the focus ring somehow.   



Mark, you have an Ioptron skytracker.  Do you have trouble with the battery cover?  It's a really tight and fiddly fit and the cover easily pops off on mine.  The other night I lost it altogether and the batteries were hanging out, luckily it did not damage the wiring.  So I ended up using parcel tape over the batteries to keep them in.  Luckily I found the cover yesterday, (I was worried the dog might have chewed it up), and so now I have the battery cover with parcel tape over it to keep it on.  Very poor design.

Carole

[Carole]

I have found some-where in the USA that makes Bahtinov masks for DSLR lenses, I am currently in communication with them.  They are not cheap, but what is cheap in Astrophotography?  These are laser cut, it's not as if you can cut one yourself as it is too fine, and if it solves a problem and enables me to do focussed widefield stuff I shall get one.

http://www.lonelyspeck.com/sharpstar/

Carole

[JonC]

Hi Carole,
Starting out with this stuff myself. At the moment I am using a £50 windows tablet, and APT. Then use the live view zoom magnifier to tweak the focus. Although my standards are considerably lower than yours.

[Carole]

Thanks Jon, I am never confident I have reached accurate focus when just doing it by eye, and having been used to the positiveness of the Bahtinov mask I really want to try to get that accuracy with lens imaging, and I am not sure if I will be able to take a netbook with me abroad or how long the battery will last, though it should work for long enough to do focus at least.

Also I didn't think tablets came with USB ports?

I am borrowing my daughter's netbook this weekend to see if I can download the Canon software onto it and see whether I can operate the DSLR and see how long the battery will last.

I can see I am going to get very little in the way of clothes into my suitcase, especially as Adrian and I are only taking one suitcase with us ATM, as I already have the tripod, and spreader going in, so if the netbook it going in as well, that's all going to add to the weight.  Might have to add a 2nd suitcase, Lol. 

Carole

[JonC]

APT does have focus aid built in, think it analysis the image to tell you when its in focus. Have not tried that side of it yet

Tablet wise the one I use is a Lenovo with a detachable keyboard, the keyboard has 2 full sized usb ports. Windows tablets tend to have either full sized or the smaller usb ports, but the smaller ones can be used with an adapter. Thing to look out for is that the tablet can be charged from a separate port, the one I have is a Lenovo Miix 3, paid £100 for it.

[Carole]

Thanks Jon,

Well I have now tested out my daughter's netbook, managed to install the Canon software and have got it working, so it will definitely help with focus if I take it abroad, so I just need to test it out to see how long the battery will last in an imaging situation.

If I can get the Bahtinov mask from the USA and it works OK, I think I will be sorted.

If I am taking it abroad, current regulations say it needs to packed in the suitcase, so will have to make sure I wrap it well. 

Carole

[The Thing]

Hi Carole,

If you are using a Canon autofocus lens, APT will autofocus it for you... I made a tiny Bahtinov mask for my Pentax manual lenses and it works a treat.

HTH and have fun.

Duncan

[Carole]

APT will autofocus it for you

So will it autofocus even without a Bahtinov mask and even if all you have are stars in the FOV (i.e.no land objects).

I am trying to make myself independent of a laptop if possible (for holidays).

Carole

[The Thing]

APT will autofocus it for you

So will it autofocus even without a Bahtinov mask and even if all you have are stars in the FOV (i.e.no land objects).

I am trying to make myself independent of a laptop if possible (for holidays).

Carole

Yes. See in the APT manual.

[Carole]

That looks very much like the focus controller in Canon Utility though it might indicate focus better than CU which you still have to do by eye which is the method Julian showed me. 

Will take a look at that for when I am using a laptop.

Carole