How to prevent Jupiter getting blown out!

[lune lupine]

Hi - very new to this astro business; only used scope twice! Tried taking a photo of jupiter using DSLR last week and could only get images of moons and white blob where jupiter should be! I've attached example below. Any suggestions what I can do to actually record some detail next time on the planet? Incidentally, even in eyepieces could not make out any details with 9mm or 32mm eyepieces provided.

I had scope out for an hour before using dslr, telescope is collimated as best as I can tell and there was no dew on lens. Telescope is evolution 8 and dslr is canon 760D.

many thanks!

[happy-kat]

Welcome, lovely telescope.

The 9mm would give x225 magnification, that may have been too much for that day's observiing quality. The 32mm would I think have shown a nice Jupiter with the main belts visible.

The image doesn't look in focus the 4 moons are too big, would expect then neat and tight in shape I think. What exposure did you use and ISO?

[lune lupine]

hmm. think i tried the 32mm but perhaps i did not. it was 5am so abit sleepy (my 4 year old woke me up at 1 then 3 that night!). Must try and and practice focus better.

Going to have another go this weekend weather permitting. is there an exposure/shutter speed/iso recommended for taking pictures of jupiter?

[Stu]

Definitely agree that it does not look focussed. The moons look like crescents brighter to one side so it does look as if your collimation is out. Can you take an image of a reasonably bright star both in and out of focus so we can see?

Once you've sorted that, it's down to exposure really, keep that controlled and you will start to see the detail. 

[D4N]

Yes the focus is definitely off, the hollow moons is a dead giveaway.

Use a bahnitov mask to get good focus on a bright star (you can make one with cardboard for nothing).

Jupiter is also very over exposed.

You will need two different exposures for the planet and the moons.

Jupiter is really bright so needs a short exposure but the moons are dim so need a longer exposure, you can combine the two in software afterwards.

[lune lupine]

boo - new scope and I thought collimation was grand when checked (albeit as a total newbie!) thought of collimating makes me a little nervous. will try and take some star shots tomorrow night and repost. Thanks

 

[Stu]

2 minutes ago, lune lupine said:

boo - new scope and I thought collimation was grand when checked (albeit as a total newbie!) thought of collimating makes me a little nervous. will try and take some star shots tomorrow night and repost. Thanks

 

Make sure you check properly before messing with anything. It might just be caused by something else but a star test is the best way to see

[Kropster]

Bahtinov mask for focusing on a nearby star first is the way to go.

Shorter exposure for Jupiter and less magnification should yield a better result.

[Yamez]

For ISO you want to keep at a minimum, whatever your cameras lowest iso is, for me it is 100. For shutter speed try 1/100th of a second, if it's too bright use a faster shutter speed, it's to dim use a sloer shutter speed. It's all trial and error. Make sure you get that focus bang on and with practice you'll get there.

If you make a video of jupiter too then you can use programmes such as autostakkert2 to stack all of the frames to produce an low noise image and then using registax 6 you can use the wavelets to sharpen that stacked image to bring out lots of detail. This again will take lots of practice and i'm still learning but with the help of this website and other tutorials it should become easier.

[cjdawson]

Here's my take.

1. You need to practice focus.  Use liveview and magnify it to 10x, that will help you to get to a good sharp focus.

The moons currently look like doughnuts, what you are looking for is for them to be nice spots, the smaller the better.

To help you focus, you might want to invest in a "Laser cut bahtinov mask".  Sounds expensive right?  Well, they're actually about £15 ish, which is kind of expensive what is essentially a piece of plastic.  But it'll help you, and will last for years.   What it does is turn point light sauces into 6 pointed stars.  When they're in focus, they look like good stars, when not in focus, you get a triangle in the middle, you adjust the focus to close up the triangle.

 

2. Collimation

Looking at the image, it's great to see the defocused stars actually as we can see the collimation.  Honestly, I'd not worry about that for a while as your collimation looks to be fairly good.  Everyone thinks it's a scary thing to do,but honestly. It's just a case of point scope to star, defocus so you get a doughnut, then make tiny adjustments to the collimation screws to make sure that doughnut is dead center.  Then switch to a more powerful eyepiece and repeat only this time less movement on the screws are needed.  When you have done your most powerful eyepiece (including barlow if you have one) then you are done.

 

3. To help with the imaging.

You don't mention which DSLR you are using, so I'm going to assume either Nikon or Canon.   There is a piece of software called BackyardEOS (or BackyardNikon) that you can use to help you take the pictures.  It's got a mode for planetary, and I'm sure it will help you to capture the images.

 

4. Exposure time.

Jupiter and it's moons cannot be photographed in the same shot.  If you get the moons, you'll find that the planet is over exposed.

The trick to getting both is to take a shot with a really short exposure, to get the planet.  Then take a longer shot to get the moons.

Then I say a shot for the planet, you are best off taking a movie something consisting of around 2000 frames!  Then run that though a program like Registax.  This will help to reduce the noise in the image and give you a high quality result.

 

5. The worst part is over.

You've already taken that first photo, and whilst you'll probably look at it and not be impressed, it is a very useful shot as it gives a lot of information.  You've already got loads of advise, and I'm sure most of what I said you've already figured out.  So get out there have the next attempt, see what you get and see how to improve on that.  After a few goes you'll be capturing Jupiter like a pro.  Next you'll have to try Saturn, and I think you'll be blown away by the result you'll get from that as the process is similar, so you'll start from a better place.

[lune lupine]

Thanks to everyone for such great advice - totally brilliant community on this site!

Have just invested in bahtinov mask based on advice above so that should be here soon to see if that helps. I presume I use for a star nearby to jupiter/other planets then pan to jupiter and fine tune? Fingers crossed its not collimation issue - someone i spoke to a while ago mentioned something called 'bobs knobs' that might help simplify collimating?

Been cloudy everyday this week so itching to get another go on the scope! Fingers crossed there may be a window of opportunity saturday evening. 

 

[Kropster]

1 hour ago, lune lupine said:

Thanks to everyone for such great advice - totally brilliant community on this site!

Have just invested in bahtinov mask based on advice above so that should be here soon to see if that helps. I presume I use for a star nearby to jupiter/other planets then pan to jupiter and fine tune? Fingers crossed its not collimation issue - someone i spoke to a while ago mentioned something called 'bobs knobs' that might help simplify collimating?

Been cloudy everyday this week so itching to get another go on the scope! Fingers crossed there may be a window of opportunity saturday evening. 

 

No.....fine tune on the star. Being a point source, it will give a more precise result.

Once focused on the star, you can remove the mask and pan to Jupiter. The focus should still be spot on.

 

 

[cjdawson]

Nope, Jupiter is much much closer than the nearest star, so much so that it is likely to effect the focus.  The best bet is to focus on one of the moons.

[michael8554]

Don't use a Bahtinov mask on a non-point source .

Now we can discuss whether Jupiter's moons are far enough away to be point sources.....

Michael

[newbie alert]

You scope will need at least an hour to cool to the ambient temp before imaging..make sure its properly cooled before messing with the collimation..sct are pretty good normally

[Kropster]

1 hour ago, cjdawson said:

Nope, Jupiter is much much closer than the nearest star, so much so that it is likely to effect the focus.  The best bet is to focus on one of the moons.

I think that the difference is lost in the mechanical and optical tolerances of the equipment and practically, they are at the same distance.

[lune lupine]

well as promised took some test shots from the garden. clouds racing everywhere so had to rush but tell me what you think. 1st star is about as best I could manage to focus on it. 2nd, as a out of focus ring to show collimation etc. 

I've ordered a b. mask so hopefully will help.

every morning for last 2 weeks has been cloudy in my neck of the woods so sadly still no chance to practice on getting jupiter right!!

[Mr Spock]

The second image shows your scope is miscollimated. The rings should be concentric with the small dot perfectly central. Adjust one or more of the collimation screws, a little bit at a time, until this happens.

[CraigT82]

Before you touch the collimation screws, are you sure you took that image whilst the star was in the centre of the field of view?  It needs to be bang in the centre for a good test of collimation so if you're not sure it was you should try it again.

[lune lupine]

1 hour ago, CraigT82 said:

Before you touch the collimation screws, are you sure you took that image whilst the star was in the centre of the field of view?  It needs to be bang in the centre for a good test of collimation so if you're not sure it was you should try it again.

as far as I can remember it was in the center all right. Boo. Collimation makes me very nervous as a raw beginner! Is there a site someone can point me too suitable for a total novice. Scope again is a nexstar Evolution 8. If it helps I've been promised something called Bobs Knobs as a present which I think can be used for these situations. Thanks again for all the help!

[cjdawson]

If you take a look at your second image there's a couple of points to note.

1. when you look at the rings, on the lower part of the ring.  There's a dark spike.  That is an artifact of the scope not having been cooled down properly.  Give it another 30 mins then check again.

2. if you look at the black spot in the image, it's slightly up.

 

All you need to do is take a look at your scope, you'll see the collimation knobs/nuts/bolts.   All you need to do is, take an image like the one above.  Then make a small adjustment to "one" of the collimation knobs.  Take another image, see the change, and if it's worse, do it.   If it's better.  Repeat the process.  Take your time and it's something that you only need to do once in a while.   It's dead easy.  Honest ;-)

[MBSteve]

17 minutes ago, cjdawson said:

1. when you look at the rings, on the lower part of the ring.  There's a dark spike.  That is an artifact of the scope not having been cooled down properly.  Give it another 30 mins then check again.

Hi,

Question about cooling down in the above comment. Are you referring to the blobby line that runs from the black spot in the center to the outer edge at about 7 o'clock? Or are you referring to the circular black line running near the edge from about 4 o'clock to 8 o'clock?

Thanks

Paul

[cjdawson]

Yep, it's the one at 7 that I was thinking about.

[lune lupine]

ok - scope has been cooled for good 90 minutes+  I've run another test shot of same star and got pattern below.

 

I can see that the central circle is leaning towards the brighter circle but is this really badly collimated or should I be able to see multiple rings within rings if you know what I mean (thinking whistfully of saturn).

I did try to focus on mars as it happens and all i could see was a blurry star like image. Presumably the collimation is to blame? Tried it with 32mm and 18mm eyepieces.

[CraigT82]

Yup your collimation is definitely out.  Good collimation is essential for SCTs so I would habea crack at collimating it, plenty of guides online and YouTube bids to help.