Realistic expectations? Star adventurer

[sza85]

Hi!

I'm curious about other's experience with this little mount, that I own. I have it for a year, and the weather was so bad around here in general that I couldn't really use it much, but when I did (with a 200mm lens, which is 300mm on an APS-C sensor), I was a bit disappointed. I read some posts where people claim that they did even 3 minute exposures with it, with light telescopes. But how? I can do 1 minute with that 200mm lens, and if I try 1m20 sec for instance, the stars start to trail (to be more specific it's not like trailing but it's like some kind of a random zig-zag like pattern they draw). I don't know if it's due to the fact that it's aluminium tripod can only handle 1 minute subs without vibration, or my polar alignment is bad, or... is this simply what I can achieve with it? I wanted to look for a used lightweight telescope to have a step further but I don't dare, even tho I see from other's posts that it can handle telescopes as well. What do you think?

Thanks in advance!

[Whirlwind]

Assuming we are talking about the non mini version, the reviews I have seen indicate that for the long exposures you need guiding.

The zig zag pattern also indicates that your polar alignment is likely off too.  

Other things to check is whether your ball head is up to the job.  Those designed for lighter loads may slip slightly as the angle changes especially if the weight is not balanced across the ball joint.  if you have a very heavy lens and your camera is connected to the ball joint then you are adding a unbalanced moment to both the ball joint and the mount.

I would start with a shorter focal length (e.g. 50mm) and then work up from there.  This will give you the opportunity to learn mount and what you need to do to get it to work as you want.

[sza85]

Thanks for the reply! It's the non mini version, yes. With a 50mm lens it's possible to take 3 minute exposures, maybe even more but I only tried 3 minute subs. I don't always use a ball head, but it's a pretty good one I have, but ofc adding it to the setup adds more instability as well. The whole setup with the ball head / laser pointer / camera / lens is around 1,5 - 2kgs, so it's well under the maximum payload. As far as balancing goes I guess that's fine, but ofc there is a chance that my PA is not that good because with lowered legs it's nearly impossible to do the PA without touching the mount accidentally, and my wedge is also a bit loose, it's even possible to set the altitude with the screw screwed in (fixed). I'm in the process of making a heavy steel tripod for it to see if it will be any better, because I'm pretty sure that the weak point is the aluminium tripod that comes with the SA.  Anyway it's very good for milky way shots with my 16mm lens, and up to 50mm, so travelling with it is fine. I only have issues when it comes to the tele lens.

[Whirlwind]

9 minutes ago, sza85 said:

Thanks for the reply! It's the non mini version, yes. With a 50mm lens it's possible to take 3 minute exposures, maybe even more but I only tried 3 minute subs. I don't always use a ball head, but it's a pretty good one I have, but ofc adding it to the setup adds more instability as well. The whole setup with the ball head / laser pointer / camera / lens is around 1,5 - 2kgs, so it's well under the maximum payload. As far as balancing goes I guess that's fine, but ofc there is a chance that my PA is not that good because with lowered legs it's nearly impossible to do the PA without touching the mount accidentally, and my wedge is also a bit loose, it's even possible to set the altitude with the screw screwed in (fixed). I'm in the process of making a heavy steel tripod for it to see if it will be any better, because I'm pretty sure that the weak point is the aluminium tripod that comes with the SA.  Anyway it's very good for milky way shots with my 16mm lens, and up to 50mm, so travelling with it is fine. I only have issues when it comes to the tele lens.

You have to be careful with payload statements.  The maximum is 5kg but imaging payloads are generally taken to be half of what is quoted as a ball park figure. Also payload can be a bit misleading because the moment on the mount can be much more important.  It might need careful balancing to get the 3 minute exposures at 200-300mm (and this might be easier with a telescope).  If you have a large weight far from the fulcrum point (and especially if not balanced) then the weight the mount 'feels' is much greater than the weight of the individual items.

[Maxrayne]

Atm I'm using the SW ST80 coupled with a Nikon D5300 body on mine. Up until last night I was struggling to balance it,  but I've used to counterweight plus a Canon 550D with 55-250mm lense to sort that and was able to get both a good balance and a decent PA. First time I've been able to push 1 minute exposures. Like you it's most likely my tripod that's the weak point in mine, so I'm keeping my eyes open for an EQ5 tripod to take it

[sza85]

4 minutes ago, Maxrayne said:

Atm I'm using the SW ST80 coupled with a Nikon D5300 body on mine. Up until last night I was struggling to balance it,  but I've used to counterweight plus a Canon 550D with 55-250mm lense to sort that and was able to get both a good balance and a decent PA. First time I've been able to push 1 minute exposures. Like you it's most likely my tripod that's the weak point in mine, so I'm keeping my eyes open for an EQ5 tripod to take it

I'm also using a Nikon D5500 so body weight is the same I guess, but my tele lens is a 200mm SMC Takumar which is metal, so that's heavier. It's just strange because telescopes are generally heavier then a lens and still some people say they are able to take 3 minute subs with these combos. Do you only use the one counterweight that comes with the mount?

[Maxrayne]

Just now, sza85 said:

I'm also using a Nikon D5500 so body weight is the same I guess, but my tele lens is a 200mm SMC Takumar which is metal, so that's heavier. It's just strange because telescopes are generally heavier then a lens and still some people say they are able to take 3 minute subs with these combos. Do you only use the one counterweight that comes with the mount?

I have been doing, yes. Last night though I added more weight at that end and it just "felt" better...Not sure if it was because I just took more time to prep than I usually have time for tbh

[sza85]

1 minute ago, Maxrayne said:

I have been doing, yes. Last night though I added more weight at that end and it just "felt" better...Not sure if it was because I just took more time to prep than I usually have time for tbh

I will try mine with more weight as well then even tho I can balance the setup with one counterweight. I tried to weight down the tripod all the time btw, maybe that also introduced some vibrations as well and it's worse to do it that way.

[Maxrayne]

11 minutes ago, sza85 said:

I will try mine with more weight as well then even tho I can balance the setup with one counterweight. I tried to weight down the tripod all the time btw, maybe that also introduced some vibrations as well and it's worse to do it that way.

I've not tried weighing mine down as yet, as I don't think I have any vibration in it. Just doesn't feel stable lol. So far the biggest issue has been balance but I think I've sorted that now

[Ken Mitchell]

I've recently bought me a 72mm for the SA, before that I was imaging with a 80-200mm f2.8 lens. Most of the time at 200mm.

I always set my subs at 120 sec at 200mm and had 80% keepers. I remember during my imaging on m81/m82 I could easy get subs from 180sec and still had over 80% keepers. I believe the direction in the sky makes a difference on accuracy, closer to the pole the more accurate. On Orion for example I could only get 120sec max. 

A sturdy tripod does make a difference. I was using a decent manfrotto for the SA and my pa kept jumping when changing scope position, so had to readjust several times. Then I started using an old telescope tripod which I converted for the SA. It gave me a lot more stability and no more readjusting the pa due to scope movements. 

At the moment with the 72mm I take 60sec subs but loose around 40% of the images, depending again on PA and position in the sky.

(I use a ff camera so that makes a small difference too)

 

Ken

 

[Davey-T]

Zig zag sounds strange, can you post a picture ?

I can do 90secs consistently with mine using a 300mm lens.

Dave

[sza85]

On 23/10/2018 at 22:51, Davey-T said:

Zig zag sounds strange, can you post a picture ?

I can do 90secs consistently with mine using a 300mm lens.

Dave

I will go out tonight hopefully and if it occurs, I will post one. BTW, I didn't use the mount in the last 3 months and now it's much harder to rotate the RA axis. Why could that be?

[Davey-T]

4 hours ago, sza85 said:

I will go out tonight hopefully and if it occurs, I will post one. BTW, I didn't use the mount in the last 3 months and now it's much harder to rotate the RA axis. Why could that be?

Sounds like the clutch isn't releasing properly, with no camera and just the weight on mine it will swing freely, ie if I rotate the weight is swings back.

Dave

[sza85]

On 31/10/2018 at 12:21, Davey-T said:

Sounds like the clutch isn't releasing properly, with no camera and just the weight on mine it will swing freely, ie if I rotate the weight is swings back.

Dave

I attached the camera and the counterweight and it turns around pretty fine, it's possible to balance it. but without it, it's still not like it was before.