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Thalestris24

Star Adventure - First Light

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Without knowing the distance between the two points and how far the SA is from the wall,  it's hard to offer a definitive viewpoint, but I would *think* that that looks pretty close. What was the SA mounted on? A tripod might have moved slightly (thermal expansion and contraction of the legs?).

On tripod on table in centre of a 12 foot square room with laser level in the dovetail clamp, start and end points about 50mm apart, did a second one that ended up about 25mm apart.

Not a very rigorous test but the first SW SA I got was running slow and not keeping up with the stars, see animation

Dave

post-21198-0-10044200-1445861839_thumb.j

post-21198-0-11029300-1445862076.gif

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Here's my test setup - a laser pen on a dovetail mount.

post-33532-0-31878700-1445869235.jpg

post-33532-0-35136600-1445869244_thumb.j

It came back to 8mm ahead of from where it started. I measured that to correspond to 4mins = 1 arcdegree since 24 hours = 360 degrees and 4 mins = 1/360 of 24 hours (1440 mins). However... I noticed that as I checked it at the 24 hour time point, it had started moving backwards so I'm not sure if it started just at that moment or had reached the mark 4 mins early. Still, it doesn't seem a big error. It says in the manual (Motor Error Status, p19) that the LEDs blink if the motor speed error is over 5% (possibly in case of weight overload). 1 deg error in 360 is only 0.28% so I guess that's within tolerance though they don't really specify overall errors. I suppose one can't expect it to be perfect. I'll have to do another test with it loaded with the scope and camera. Maybe just an hour's test or possibly a 12 hour test. I think I'm still more concerned about the play in the RA axis - I can move it back and forward slightly without a lot of effort but I might be expecting too much - it might just be the play in the servo motor. Pity they don't provide any info about making adjustments....

Louise

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I think I'm still more concerned about the play in the RA axis - I can move it back and forward slightly without a lot of effort but I might be expecting too much - it might just be the play in the servo motor. Pity they don't provide any info about making adjustments....

Louise

I agree- you probably are expecting a bit much of it? The SA is designed as a portable setup for use with camera lenses and short focal length scopes.

.

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I agree- you probably are expecting a bit much of it? The SA is designed as a portable setup for use with camera lenses and short focal length scopes.

.

Well, reviews suggest it can be used for 2min subs at 400mm unguided so I'd have thought it would be even better guided?

I'm just running a loaded 1 hour point to point test. I expect it will be ok.

Louise

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True, but reviews are just that- a review of a single example of a product. Plus, when did S@N ever give a product anything less than a 4 star result? Their reviews are about as soft as you can get IMHO.

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True, but reviews are just that- a review of a single example of a product. Plus, when did S@N ever give a product anything less than a 4 star result? Their reviews are about as soft as you can get IMHO.

True... Though someone here has run it with an SV80 and apparently got better performance than I have (so far).

My 1 hour loaded test wasn't so good - it arrived at the destination point about 5 mins early! Will try again after re-balancing!

Louise

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Just want to check that the right thing is being measured here. 4 minutes early does raise the prospect we are looking at measuring sidereal day against a solar day, or has that been taken into account?

Edited by MattJenko
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Just want to check that the right thing is being measured here. 4 minutes early does raise the prospect we are looking at measuring sidereal day against a solar day, or has that been taken into account?

Hmm... The SA obviously tracks at a sidereal rate so I suppose 1 revolution = 360 deg corresponds to a sidereal day so I think you're quite right and it would arrive 4 mins earlier than I'd originally thought it would. That's good cos it means it was actually spot on! :)

Thanks for that, Matt!

Louise

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True... Though someone here has run it with an SV80 and apparently got better performance than I have (so far).

My 1 hour loaded test wasn't so good - it arrived at the destination point about 5 mins early! Will try again after re-balancing!

Louise

Hi Louise,

That is pretty close... don't forget a siderial day is 23hrs 56min 4.1secs... not 24hrs... so 5 mins early is not far out.

What is the normal running current in the specification sheet?... USB2 can only supply a max of 500mA and some PC/laptop ports are limited to 300mA.

I have been looking at one of these myself recently for an easy grab and go setup.

Keep Happy.

Sandy. :grin:

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What is the normal running current in the specification sheet?... USB2 can only supply a max of 500mA and some PC/laptop ports are limited to 300mA.

They also have a battery compartment for 4 x AA batteries.

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Hi Louise,

That is pretty close... don't forget a siderial day is 23hrs 56min 4.1secs... not 24hrs... so 5 mins early is not far out.

What is the normal running current in the specification sheet?... USB2 can only supply a max of 500mA and some PC/laptop ports are limited to 300mA.

I have been looking at one of these myself recently for an easy grab and go setup.

Keep Happy.

Sandy. :grin:

Hi Sandy

The manual doesn't mention current - just that it will run continuously for up to 72 hours on 4 x AA batteries. Says it will run from usb and mine seems quite happy with usb power. I think my usb supplies 500mA (I think I actually have it plugged into a desktop usb 3 port).

Louise

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Your test setup looks a lot more professional than mine Louise :)

When I originally said 24 hours I really meant a sidereal day  :rolleyes:

No play at all in my RA perhaps you should take it to bots and have a look see.

Dave

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Your test setup looks a lot more professional than mine Louise :)

When I originally said 24 hours I really meant a sidereal day  :rolleyes:

No play at all in my RA perhaps you should take it to bots and have a look see.

Dave

Hi Dave

I just happened to have the laser pen bracket that I got from Rother Valley Optics a long time ago - knew it would come in handy one day!

Well, I suspect there is some RA backlash that could maybe (in theory) be trimmed and minimised. However, I don't want to invalidate the warranty if I can help it.... Wish Synta provided service info for their products... Anyway, I'll test it again when the opportunity arises - cloudy here now :(

Louise

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Hi Sandy

The manual doesn't mention current - just that it will run continuously for up to 72 hours on 4 x AA batteries. Says it will run from usb and mine seems quite happy with usb power. I think my usb supplies 500mA (I think I actually have it plugged into a desktop usb 3 port).

Louise

Hi Louise,

Ok, thanks for the info and I hope you can tame yours to your satisfaction.

Keep Happy.

Sandy. :grin:

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Hi Louise,

Ok, thanks for the info and I hope you can tame yours to your satisfaction.

Keep Happy.

Sandy. :grin:

Thanks - so do I!

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I've been doing some more daytime experiments on the SA, as it's been awful weather up here. I decided there was probably too much load on it. The scope, camera, finder guider, counterweights and mounting hardware came to ~6.5kg. It was way off on the point to point laser tests (done with a laser in place of the finder guider) so lighter than it would otherwise be in use. The payload for the SA is 5kg max. However, the dovetail l-bracket and counterweight are optional extras so probably need to be counted as part of the payload. So, I've substituted the Travel Scope 70 for the ST80. The former is a lot lighter than the ST80 and has also allowed me to ditch one of the counterweights. However, I've had to add a ball head to mount the laser/finder guider and the scope still needs a 1kg ankle weight to balance it in DEC, so the setup is still a bit on the heavy side. Anyway, this new setup seems to be performing better on point to point tests (spot on, over 3 hours forward and reverse). Dunno when I might get a clear enough sky to try it out in anger again. There is a possibility of a short clear period from 11pm tonight but that's a long way off!

I think I might start tweaking the 130pds tomorrow - I've been putting that off for weeks!

Louise

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Hi all

I was able to do some more testing last night (albeit by the light of the silvery moon...). Actually, this was also first light with the TravelScope 70 as an imaging device. Things were slightly improved, I'd say, though the guided RA is still the source of larger errors than the unguided DEC. However, I don't understand why I get a big difference in the RA trace between the PHD2 graphs comparing unguided vs drift aligning. Surely in both cases the mount is unguided so should produce similar graphs - or am I missing something?

Here is an initial 6min drift align (Alt):

post-33532-0-50193600-1446119350.png

But here is an unguided graph (573 secs):

post-33532-0-81939100-1446119456.png

Big difference with the RA trace! Why???

Anyway, here are some single subs, all taken with a 550d, ISO 400, ccd-cls clip, F5.7:

30s:

post-33532-0-06658600-1446119663_thumb.j

60s:

post-33532-0-97620600-1446119701_thumb.j

90s:

post-33532-0-52932900-1446119725_thumb.j

120s:

post-33532-0-00680900-1446119782_thumb.j

Here is guide graph to go with last, 120s, sub:

post-33532-0-69261400-1446119886.png

I decided to be more ambitious and try some longer subs (at F9.5):

240s:

post-33532-0-02388600-1446120095_thumb.j

Crop:

post-33532-0-61041700-1446120137_thumb.j

Guide graph:

post-33532-0-86378200-1446120206.png

300s:

post-33532-0-71122200-1446120273_thumb.j

Crop:

post-33532-0-10117600-1446120299_thumb.j

Finally, did another 5min drift align (then clouds came in):

post-33532-0-56447000-1446120397.png

I suppose not too bad overall. Focus might have not been optimum. Terrible CA with the TravelScope though! But a better 70mm scope is going to be a lot heavier... Maybe a 60-65mm scope? (though I don't want to spend a lot on another scope...). Suggestions welcome!

Louise

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Hi Louise, I've never tried guiding mine so no idea how it would perform, will try to fit in a test sometime to see how it compares, you and I have a different plan for using the SW SA , I got it solely for a grab and go to dark skies using DSLR and camera lenses up to 300mm and capturing to the SDHC card, no laptops or power packs involved.  I assume you want yours as an easy to carry up and down stairs imaging rig using some sort of scope and longer guided exposures.

Not sure if that is what it was designed for, it really excels at widefield Milky Way images and timelapses.

What Dec were you imaging at, were you using a LP filter ?

Dave

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Hi Louise, I've never tried guiding mine so no idea how it would perform, will try to fit in a test sometime to see how it compares, you and I have a different plan for using the SW SA , I got it solely for a grab and go to dark skies using DSLR and camera lenses up to 300mm and capturing to the SDHC card, no laptops or power packs involved.  I assume you want yours as an easy to carry up and down stairs imaging rig using some sort of scope and longer guided exposures.

Not sure if that is what it was designed for, it really excels at widefield Milky Way images and timelapses.

What Dec were you imaging at, were you using a LP filter ?

Dave

Hi Dave

Yep, to go up and down stairs with! I have a Canon 75-300mm lens but it's no good for Astro. I don't want to spend on another fixed lens. It's supposed to work ok at 400mm or more... I don't particularly want to do very widefield shots though I'd still consider 400mm as 'widefield'. Not sure about DEC - it was a random piece of sky in the east - quite low down. Yes, as mentioned above, I was using a cls-ccd in the 550d.

Louise

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It might be worth scouring eBay for a cheap prime M42 lens. Some of them are optically very, very good and you can find decent focal lengths (~200mm) at pretty fast focal speeds.

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It might be worth scouring eBay for a cheap prime M42 lens. Some of them are optically very, very good and you can find decent focal lengths (~200mm) at pretty fast focal speeds.

Hi

I already have a Super Takumar 200mm but I want to use a longer focal length... Maybe I should have got an eq5 pro but I think it would be too heavy for me to carry up and down the stairs. I might bite the bullet and undo the SA to see if I can adjust the RA backlash. The unguided DEC is fine - over 4-5 mins it's better than my guided DEC on other mounts, lol.

Yes, that was a very nice image of M100 @ 432mm - so it can be done! Unguided too.. I get the impression he has quite dark skies in his garden... Also, the scope is ~2.5kg? I'd probably be into overload again with a guider though maybe the Lacerta is easier to balance? A Lightwave is another possibility. The trouble I have is that from my urban location, and with the lp filter, I really need to do longer subs than Tommy's 2mins. Admittedly, only single subs, but you can see from above what I get at 240s and 300s. It may be that I can improve the balance and that will then improve the performance in RA. The SA is awkward to balance...

Full Moon tonight...

Louise

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Hi Louise, just wondering how you calibrate PHD does it fail Dec calibration or can it be set to calibrate RA only. ?

Only asked about the CLS clip filter as I found it produces those red / blue haloes making it hard to focus don't know if this is aggravated by CA , I've found the IDAS LP filter better but I know you don't want to spend more money.

Reading Stephens link Tommy Narwatil seems to have success with a fairly heavy setup.

Some folks apparently looking to mod the Dec adjustment to motorise and guide in Dec.

Dave

Lacerta weight is stated as Kg 6.00 on 365 site

Edited by Davey-T

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Good luck louise.

I can't help thinking that you might be pushing the wee SA too hard though. I couldn't really envision trying to image at 400mm with this mount...it's just too light for my clumsy setup attempts. Perhaps looking into something like an Astrotrac would be a better option? I have also heard good things about the new Fornax Lighttrack system- a friction driven portable mount:

http://www.365astronomy.com/FORNAX-10-LighTrack-Mark-II-Mobile-Tracking-Mount-for-Astrophotography.html

365 Astronomy also have stock of the earlier version of the Lightrack at £299:

http://www.365astronomy.com/FORNAX-10-LighTrack-Mobile-Tracking-Mount-for-Astrophotography.html

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