fun with tablet and DSLR

[GraemeC]

>Yes I get live view but the stars didn't show up, you can magnify the image, Jupiter might have shown but the clouds rolled in before I found it with the tripod. My tablet brightness is very turned down have to raise it next time in case that played a part.

Try the free shutter release app first to make sure your tablet can run the program with your camera.

The main app has full camera control and very quick to make setting changes. Manual focus has really good control using the buttons on the screen.

I use live view on my canon dslr with good results, but there is a technique. In order to focus I make sure it's pointing to one of the brightest stars or a planet first. Betelgeuse is easy at the moment as its close to where I point the camera for the longer exposures. Turn on live view and the screen is dark. But that's not a problem, it's just the screen is too small to show it. Increase the live view Magnification to 5x. Then you will see your target star, dead centre . If it isn't in the centre adjust until it is. Then go to 10x and you will see the round red blob of Betelgeuse. Carefully adjust the manual focus until it is pin sharp. Job done!

Graeme

[happy-kat]

If this rain stops I will try that next time thanks for the tip.

[Ags]

I tried the free shutter release app on my asus memo pad, but it tells me I would need to root the tablet to (maybe) get the app working. So the full DSLR Controller app is a no-go for me.

[knobby]

<a class='bbc_url' href='https://play.google.com/store/apps/details?id=com.dslr.dashboard'>https://play.google.com/store/apps/details?id=com.dslr.dashboard</a><br />

<br />

Try this one , its free and doesn't need root access

[happy-kat]

Managed a very quick use of one of my vintage lens tonight, the 55mm f2.

Whilst it has an infinity focus mark focus was achieved slightly in from the full stop.

Using my Nexus to preview the images (not taken them off the card yet) even at f2 it looks promising for star shapes being good right to the corners and edges (well good enough for my untrained eye). This is the lens where when fully open there is very little lens wall left.

Because Orion was so much higher now it was 5 seconds only I could manage (might have been less when I check the files) before star training appreared but this lens picked up way more stars I thought than the kit lens.

So a better slightly longer session will be interesting to actually capture more than a handful of test images to compare to my image from the kit lens.

[Alien 13]

Managed a very quick use of one of my vintage lens tonight, the 55mm f2.

Whilst it has an infinity focus mark focus was achieved slightly in from the full stop.

Using my Nexus to preview the images (not taken them off the card yet) even at f2 it looks promising for star shapes being good right to the corners and edges (well good enough for my untrained eye). This is the lens where when fully open there is very little lens wall left.

Because Orion was so much higher now it was 5 seconds only I could manage (might have been less when I check the files) before star training appreared but this lens picked up way more stars I thought than the kit lens.

So a better slightly longer session will be interesting to actually capture more than a handful of test images to compare to my image from the kit lens.

Most of the old lenses where designed for a full frame 35mm camera so they do perform well with a modern croped DSLR sensor.

Alan

[happy-kat]

ah I see so the edges are already cropped from view so to speak as the senor can't 'see' them, I like that thought.

[happy-kat]

This single shot was taken with the vintage lens which is a 50mm after all, I think this is one partial stop in from full wide so I guess f2.2

iso800 and 6 seconds, still a smidge of star trails showing.

But even compared to the image at the start of this thread which was 8 seconds with the kit lens there are loads more stars showing so this vintage lens looks to be quite an improvement on what was captured and it was cloudy.

[Psychobilly]

Pentax changed from M42 to  the bayonet K mount  so if a lens is just described as Pentax  fit it's worth asking what type it is...

Peter...

[Alien 13]

Great image.

If you factor in the canon crop factor of 1.6 the 50mm lens is more like an 80mm so you need to calculate star trails based on that.

Alan

[happy-kat]

I have both a m42 and a pentax k mount adaptor as I have one of each lens. The 28mm is pentax k mount though I have not tried this one yet.

This image Orion was much higher in the sky then when I used the kit lens so I guess that was a factor too as both lens were more or less the same range.

I guess on that I should have used 5 seconds on the 400 rule

[JamesF]

If you factor in the canon crop factor of 1.6 the 50mm lens is more like an 80mm so you need to calculate star trails based on that.

It's still a 50mm lens.  It's just that the field of view is approximately the same as you'd get with an 80mm lens with a full-frame sensor.

James

[Ags]

Yes, and because the field of view is narrower, the star trails appear proportionally longer! They are the same as the star trails of an 80mm lens on a full frame camera. If it takes 90 minutes for a star at the equator to trail across a crop sensor at 50mm, it also takes the same star 90 minutes to trail across a full frame sensor at 80mm (because the sernsor is physically larger).

[JamesF]

Yes, and because the field of view is narrower, the star trails appear proportionally longer! They are the same as the star trails of an 80mm lens on a full frame camera. If it takes 90 minutes for a star at the equator to trail across a crop sensor at 50mm, it also takes the same star 90 minutes to trail across a full frame sensor at 80mm (because the sernsor is physically larger).

True enough.  But if you want to avoid star trailing, surely it's not relevant information?  What matters is the actual focal length and the pixel size of the camera.

James

[happy-kat]

Last night I tried M 44 with the Canon 1100d on my tiny tripod connected to Nexus 7.

Beehive cluster taken using vintage 50mm lens f2 4 seconds ISO 1600 16 lights and 13 darks. Slight tweak in levels. Edge of a town with significant local light polution.

Before I uploaded it did not look like it needed croping but it obviously does now, whoops.

[Alien 13]

+1 for the golden oldies lenses i mean..

Alan

[happy-kat]

I love that the camera saw what I could not see and I even recall tring to see this with bins last year and only managing with iverted vision.

The lens though is very likely to be midly radio active on researching which lens it was!

The kit lens has not been on the camera since though this old lens is pretty heavy.

I only imaged this because I had managed to locate it in the ST80 by hand so thught have a go with the camera.

[Alien 13]

My Asahi pentax lens is radioactive the glass is a bit yellow now but nothing a few weeks in the sun cant fix.

It is amazing that even a couple of minutes exposure though a lens can show stuff thats imposible with most amature scopes.

Alan

[happy-kat]

Thank you for reminder about UV can fix any yellowing though this lens seems quite clear of colour when I look at it.

I have too many commitments for the next couple months but I can't wait till I build a barn door tracker to use with it.

Same make mine is a Super Takumar Asahi Opt Co. Made in Japan 1963 or 4 I think my research indicated.

[Russe]

How do you guys focus your lenses? Trial and error or do you use masks similar to a Bahtinov??

[happy-kat]

With it is connected to the tablet I face the camera to a bright star get this viewing on the tablet, do a 5x and then 10x zoom on tablet and can then turn the focus ring till the star is a clean neat cicrle. That is then focused. I don't touch the focus ring again and drop my black cardboard light shield around the lens held on with an elastic band.

This lens infinity is not at the lens stop so I have to do it manually but with the larger screen on the tablet it works out fine.

The tablet works like a giant live view screen.

[Alien 13]

How do you guys focus your lenses? Trial and error or do you use masks similar to a Bahtinov??

I just used the magnified live view with the iso pushed up then focus on the dimmest star in the FOV its much more obvious if focus is correct that way because the star will go from invisible to visible with nothing in between.

Alan

[frugal]

How do you guys focus your lenses? Trial and error or do you use masks similar to a Bahtinov??

For focal lengths above about 200mm I used a Batinov mask (it does not give diffraction spikes below 200mm). I still need to use a 5 second snapshot in Backyard EOS in order to get those spikes.

For wider angle focal lengths I use the FWHM function in Backyard EOS, but I still need to use the snapshot function most of the time. My skies are not dark enough to use Live View in real time.

[happy-kat]

So after loosing OTG support with 4.4.3 and 4.4.4 and not receiving any OTA updates and just on the edge of rooting my tablet I notice File Explorer was working fully so I tried the camera connected again and bingo every thing is working again as it should. Yet no OTA update that I am aware of from Google. Not comlaining.

So no rooting needed but will see if I do it anyway to take the opportunity for a clean install and adding custom recovery boot loader.

[happy-kat]

I remember now there was a security patch last week, so brilliant got OTG support back again. Very pleased.

Reading my thread again reminds me I have a 28mm lens yet to try on the camera, bonus though the apperature blades do not pull back anywhere near how much they do with the 50mm.