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Summer Triangle Challenge

First impressions of the Skywatcher Star Discovery p150i

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The brief was to find a telescope that wouldn't be so big that my wife would object, whilst ensuring good all round visual image capabilities. I settled for a 6 inch reflector on a GOTO, having discounted larger OTAs (nowhere to store at home, at least whilst testing the waters for a new hobby). Altaz mounted GOTO felt essential due to living in a Bortle 8 city area in which even a star like Polaris on a perfectly clear night seems barely visible so limited opportunity to learn star hopping. Plus having experienced some beginner Dobsonian telescopes at a recent public observatory I felt a little frustrated at the thought of having to look for a feint smudge in the streetlight-filled sky only to lose it to the Earth's rotation a few seconds later.

The SDi150p comes in two large cardboard boxes and assembles pretty easily. My initial thought was that the azimuth rotation felt very stiff compared to the (adjustable via dial) altitude rotation, and I wondered if it was even intended to be manually pushed. Subsequent posts suggest the opposite can happen in operation and if the azimuth clutch becomes too loose the GOTO fails to position correctly. We'll see.

The OTA is a deep red - not my favourite colour but blends well with my red LED headtorch. It's quite lightweight and easy to carry when off the scope. However, the tripod needs a bit of disassembly to fold as the brace that doubles as a lens holder has to be unscrewed first. I have to carry the scope around 100m to get to the centre of a large park nearby with good protection from streetlights and no trees in the way. I'm debating whether it's better to carry the scope and tripod in separate hands (using straps for the scope, and maybe or maybe not folding the tripod - it needs to be in a single trip), or whether to carry the scope attached to the extended tripod, lugged over my shoulder. I did that last night and it sort of worked but felt clunky and only just got the tripod through the front door. How do you carry yours?

Controlling the scope is entirely by mobile phone app. Simple to find my way around, though wasn't always sure if pressing the "move" buttons actually did anything after landing on a star. One very simple trick I found was to turn my phone 90 degrees to landscape when looking sideways through the eyepiece - that way the controls are oriented to the viewfinder so if I press the "down" button the star moves down, and if I press "right" it moves right etc. Whereas if I hold my phone landscape and look through the red dot finder the button "down" obviously corresponds to a movement down etc.

First attempt wasn't great though it was on a grassy field and I doubt the tripod was totally level. The GOTO seemed to have problems deciding where anything was and took me to maybe a degree of what I was looking for but no better.

Second attempt, last night and I mounted the tripod on a concrete path then levelled it using a spirit level. What a difference! Much better GOTO performance, though it seems that even after two star alignment if I move to something else, it may be bang on the centre of the eyepiece, or it might be half a degree off or so. Is it possible after centring a point object, to use the newfound object to improve the alignment accuracy further? I can't find three star alignment in the Synscan phone app menu.

Incidentally, I'm using 1.5V 2800 AA rechargables at the moment. Could anyone who uses this mount advise how many hours I can expect from them, and if it's worth getting a powerbank, what type to go for? The Celestron powerbanks are in excess of £100 which may be hard to bite after everything else so far, especially when rechargeable lead acid 12V power supplies appear to cost a fraction of that.

The other quirk I noticed is that when tracking stars if felt like the scope was tracking them, but maybe not so good when tracking planets. Unless planets are supposed to track at a different speed? Anyway, they seemed to shoot out the eyepiece much sooner than stars. Any suggestions?

Finally, optical quality. I haven't used the 25 or 10mm lenses as I went for a 7-21mm Skywatcher zoom. It's pretty lightweight but gives me pretty sharp images across the range of magnification. I also got a 2x Baader and the Moon looked astonishing at 3.5mm (214x magnification). I struggled a bit to focus on Mars (as others have commented, the focuser is a bit of a let down though necessary at this price point, it's possible to get really good focus but you have to be really careful how you do it). I cheated for Mars at high power - I first went to the Moon and focussed at high power. Then I went to Mars - nowhere in the viewfinder. Switch to 21x (with Baader) - there it is so recentre WITHOUT refocussing. Then zoom in to 7mm / 3.5mm again and it's centred and in perfect focus.

The "tonight's highlights" was quite a useful list of clusters, nebulae and double stars, arranged from brightest downwards. Surprisingly many were very low in the horizon, around 6 degrees or so and below the distant tree line. Most were in the north western sky which I wonder was because the Moon is close to full and lightening half the sky at the moment. I maxed out at a magnitude 7 fuzzy object. Actually there were several fuzzy things in the frame, not sure which I was meant to be looking at. But I guess nebulae aren't easy to see in Bortle 8 areas. The double stars were incredible, and I had a go at the Beehive cluster and a few other clusters I had never previously heard of, absolutely magical stuff. I might only have been outside for an hour but saw more up that scope in one hour than I've seen in the sky the whole of my lifetime prior to last night.

Sure it has a few compromises. And I guess if it gets me excited enough to persuade my wife to let me upgrade to the 500mm Flextube in a few years' from now I'll have a clearer idea of what more to look for. But I can easily see this being a fantastic entry point to learning a new hobby.

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Nice report. My own 150i has been a great companion on the learning journey.

7 hours ago, Starfazed said:

How do you carry yours?

I only have to get mine to the end of the garden, but I take the OTA separately. I leave the mount and tripod connected, as they are a bit fiddly.

7 hours ago, Starfazed said:

levelled it using a spirit level. What a difference! Much better GOTO performance

I always level as best I can, though some day it shouldn't matter.

7 hours ago, Starfazed said:

Is it possible after centring a point object, to use the newfound object to improve the alignment accuracy further? I can't find three star alignment in the Synscan phone app menu.

Three star alignment is available for equatorial mounts, to correct "cone error" - stick with two star.

The initial alignment gives a "whole sky" model, but you can use further stars to refine the gotos in a specific sky area, if you are looking for several targets in the same constellation, for example. They used to be called "pointing accuracy enhancements", not sure if they still are, and are described in the manual.

7 hours ago, Starfazed said:

I cheated for Mars

I do this myself. Mars is now small, and not easy to focus on, especially in indifferent conditions.

7 hours ago, Starfazed said:

many were very low in the horizon

There is an altitude limits option in the settings, which (when the catalogue filter is set on) does control some aspects of behaviour like goto. It may also filter the suggestions list.

7 hours ago, Starfazed said:

I guess nebulae aren't easy to see in Bortle 8

Yes, you'll be challenged by the fuzzies. Doubles, the moon, planets, some own clusters and planetary nebulae will be better suited.

7 hours ago, Starfazed said:

now I'll have a clearer idea of what more to look for

Precisely. Learn the sky, learn the craft. Try out other people's scopes when you can. Then you'll be well placed for your next purchase.

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  • 2 weeks later...

Lovely to read your report. The star discovery mount has freedom find so with the clutches loosened the mount can be moved by hand manually with no power useful if batteries go flat when out. Once aligned freedom find means if the telescope is knocked when say viewing then can select the target again and the mount is able to slew to it again. When aligning the mount tends to automatically select a slower slew speed but you can choose a different rate whenever you like on the app the rate is shown in the centre of the movement arrows pad and can be adjusted with the little left and right chevrons. While in use if you centre a target in the eyepiece after a goto action you can confirm the position this adds to the goto accuracy.


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