Short Comparison Skywatcher Mercury 705 Orion ShortTube 80

[happy-kat]

Took delivery of the Az3 mount from FLO I picked up in clearance and it came with a Skywatcher Mercury 705 which I will be lending to a collegue with two small boys (the OTA only).

The mount, for what I wanted it for it is perfect and I can view almost zenith fine and the weight of either of these tubes is easy confortable and it does not slip pisition and is steady and well dampened but I extend the legs just a foot as I sit to observe. Even observing on decking which wobbles if you breath deeply was not an issue at all with image wobbling.

The Mercury is a 70mm aperature and built reasonably nicely, quality wise the Orion is a better build and this mainly pertains to the focuser. The Mercury does have a r&p but there feels slightly too much softness in the turn so stopping at focus does not feel crisp. I will look tomorrow to see if there are any alan key holes to tighten up the feeling. I have made no modifications to this Mercury tube.

The Orion I have reviewed elsewhere and shared that I have blackened the edges of the doublet and blackened the inside of the top half of the tube.

I wanted to test the Mercury on Jupiter before I lent so I knew how it performed. Using the provided 10mm I was pleasantly surprised to actually see two main bands and the scope handled my WO SLP 6mm pretty cleanly too and the image stayed reasonably defined. Jupiter's moons were nice and clear.

CA, OK on general stars it was not present but on Jupiter it was pretty bad and at times was more than a halo on a limb but an actual blob of CA. I could still see Jupiter so overall it was useable and you could forgive it for a basic starter tube.

Within about 45 minutes (after eating) I then took the Orion out on the same mount. This is the first time I have used the Orion on a tripod and it is a darling to use.

On Jupiter with 32mm there was no CA nor was there any with my 16mm. I then put in the WO 6mm and there was just a small amount with was often just a hint to also being none at all. Whether this very little CA is down to my modificaitons I wont know as I was umable to do a before on Jupiter.

So at the end of this I would say that the Az3 with the StarTravel 80mm is probably worth the shlight extra in price over the Mercury 705 plus you get a bit mroe aperature. This is on the assumption the StarTravel is the same as my Orion.

I need to next work out how I can cheaply (free) modify the Mercury to fit on a camera tripod as the current thread holes on the tube rings are not photo tripod size.

[Russko13]

Have you any experience with the skywatcher evostar 90mm? I only ask because I'm getting one in 2 weeks a birthday gift

[happy-kat]

No I haven't but when I have read stuff on your bithday present it it has been favourable and you have a great focal length for planets on it.

I expect you can't wait for it to arrive.

[happy-kat]

So today I have taken the lens out of the Mercury and blackened the edges and also re blackened the inside top half that I could reach and any shiny bits. So will be interesting to see if this improves Jupiter.

Focuser tension also improved, the knob had taken off in the box.

I did have trouble getting the bigger lens out it was slightly stuck which might have meant they were not seated correctly.

[happy-kat]

It was time to assemble it all again as given oodles of time for the paint to fully dry.

I had thought I might need to take the Dremmel to the plastic lense cell carrier as the bottom lens was very tight and really took a while to get it out.

Though on puting the lens back in the bottom lens popped into place fairly easily so no Dremmel required which is good as I had fears this could have upset the collimation.

Initial testing on the trees about 500 yards away and this time (OK I admit the sun is not out brightly as it is overcast today but I am pointing NE so the brighter part of the sky and I am gob smacked there is no CA showing on the fine branches (25mm).

On my first test when lining up the RDF the CA was really very strong on these same branches, unlike with the ST80 where the CA only showed on the photos I took using my DSLR on the same branches.

Hopefully there will be some clear sky tonight so I can check for star shapes, optic pinching and CA oh and line the RDF back up again.

[Alien 13]

Ive allways fancied the mercury as a finderscope and you get a free AZ3 with it.

Alan

[Russko13]

Sounds like your certainly gonna get the most out of those scopes! I'd be too worried about damaging the optics or not being able to put it back together right lol but hey that's just me I'm no engineer!

[happy-kat]

I am not an engineer either, work with software, but I do love knowing how things work and spend lots of time researching and making sure I am prepared before I start.

I'll post an update when I get to retest the Mercury at night, I have a feeling tonight is a cloudout.

It is quite long with the dew shield on so not sure if that matters with the idea of it being a finderscope, but it sure is very light and is free really with the tripod which I am very happy with. I will fashion a counter weight for using the ST80 and my DSLR as I slackened the altitude nut to suit me and it wont hold with the extra weight but I wont use the camera that often I don't think so not a problem for general use. I have not had any problems with tripod tipping even with the ST80 and dslr and it pointing as vertically as it could on 2/3 extended legs. I can position the ST80 quite forward though more so then if it had tube rings I think using the inbuilt dove bar and using the camera mount attachment for the tripod.

[happy-kat]

Managed to get 20 minutes between the clouds tonight. Very wet air.

What I noticed was that the CA was less pronouced to what it had been when I used it before the changes. I used the supplied 10mm and whilst it is obviously still there it was not as bad as it had been the big overlaying splodges were very tamed to not being there so was left with the edge brightness CA on Jupiter but equally as seen on the other scope moving the eye around could see it disappear as much as appear.

Star shapes were quite neat even to the edges though not as neat at the edges as in the ST80, on this scope they sort of broke up more but did not stretch out in length.

I did have refraction spikes on Jupiter and I need to research why this might have been I have seen this on the Heritage so I am hoping this was due to the wetness in the air rather than anything more sinister.

Also need to research if normal when defocused fully to see the edge of the lens and make out the three spacers. I also had a thin black line go straight across the view when fully defocused like this, also apparent in the 25mm but in a slightly different location.

Defocused star shapes were neat and not three sided which I gather might have indicated pinched optics.

All in all it is improved I feel from my first viewing especially as on that day the view in the ST80 was cracking so I know that today in poor conditions it looked better.

[Alkaid]

I also had a thin black line go straight across the view when fully defocused like this, also apparent in the 25mm but in a slightly different location.

Are you using a prism diagonal? I had a very poor one for terrestrial viewing and whilst it's acceptable for this purpose, I did not use it for astronomical purposes due to this 'line effect' and also some light scatter when looking at bright objects. Might also explain the diffraction spikes?

Using a mirror diagonal should not exhibit any of these issues, they are superior for night time viewing.

[happy-kat]

Thank you.

Using this here it was real bad atmospheric turbulence and not pinched optics.

I guess as it is the free supplied one with the scope it would be a prism.

How could I tell just by looking at the unit please?

[Alkaid]

Thank you.

Using this here it was real bad atmospheric turbulence and not pinched optics.

I guess as it is the free supplied one with the scope it would be a prism.

How could I tell just by looking at the unit please?

Set up the scope during the daytime and look at the view through the eyepiece.  If the view is upright and correct, then it's a prism.  If the view is upside down, then it's a mirror diagonal.  Also, the prism diagonals tend to be cranked at 45 degrees.  The mirrored ones tend to be cranked at 90 degrees for easier astro-viewing.

The mirrored ones give a much better view as the light is just reflected.  In the prism, it is refracted with glass.  The glass is often not as good quality as the glass used in the telescope lens.

[happy-kat]

The view was the right way up so that makes a prism it's a 45 degree jobby.

I also have a 90 degree one I will take a punt using that in the AT80 to see what way the image orientates.

[Alkaid]

The view was the right way up so that makes a prism it's a 45 degree jobby.

I also have a 90 degree one I will take a punt using that in the AT80 to see what way the image orientates.

Good stuff. It'll be upside down in the 90 degree one, but you should notice a better quality image. The orientation of the view does not matter as there is no up or down in space!

[happy-kat]

My 90 degree I think was the same way up but anyway there was no line showing so that was good and proved not my tinkering

Tonight the sky was like chalk dusted but the turbulance was quite still and I had a pretty clear view of Jupiter in the 70mm and as it was not bright the CA in my 32mm and 16mm was none existent. In the 6mm there were faint hints of it but easy to not notice it and the middle bands and even at each cap were pretty clear. The provided 10mm the CA was much more evident.

I followed Jupiter's moons to the edges and the shape stayed true right to the end so pretty crisp across the entire fov. Right at the very edge the CA suddenly became very apparent but who looks there anyway,

So conclusion I am very happy with the mount and can live with it's quirks as you can end up with a fine adjuster up your nose.

The scope whilst only 70mm with what I have been able to see is not that bad and a start into looking up.

The setup does benefit from an imrpoved high power eyepiece to bring out the best that the scope can do.

Probably worth doing the tinkering too.

Pleased with my bargain.

The scope is going to be loaned out.

[Alien 13]

I do like small scopes 70 or 71 mm is a good size.

Alan

[happy-kat]

Aesthetically I love my ST80 in white and the all metal feel and coolness. Why that scioe is bundled with the Eq1 I have no idea as the mount surely is enough to put a starter off.

[Alien 13]

Aesthetically I love my ST80 in white and the all metal feel and coolness. Why that scioe is bundled with the Eq1 I have no idea as the mount surely is enough to put a starter off.

 

I would agree the AZ3 would be much more useful.

Alan

[Alkaid]

Or AZ4....love that mount!

[happy-kat]

The az4 has no slow motion controls and I am enjoying using these on the az3 and given I already have the dob too I did not want a dob on stick legs.

[Speedy]

Have you any experience with the skywatcher evostar 90mm? I only ask because I'm getting one in 2 weeks a birthday gift

I have one of these ...well its a Helios which is now skywatcher so I assume its the same....great scope took this pic the other night through it by holding my phone to it

[happy-kat]

With more exprience under my belt I wanted to add:

love my AZ3.

I have since learnt to observe bright objects with just the centre cap removed to reduce CA.

Better quality eye peices make a big difference particularily for the shorter focal length.

What a bargain the Mercury 705 is still with the AZ3 with our site sponsor.