Drifting when viewing

[greencode]

My first night viewing the night sky with my new Heritage 130p. Really enjoyed it before the clouds descended. The thing I could figure out is one second I had the moon, for example, in the centre of my viewfinder and then the next second it had drifted. I've got everything tightened on the dobsonian mount.

Is this actually me being a bit stupid here and ultimately because it's zoomed in so far (25mm with 2 x barlow) that in actual fact it's just everything moving i.e. the world, the planets etc?

Sorry for probably a very silly question - expect lots more in the coming weeks ;-)

[catman161]

Yes, it is the earth moving that makes the moon and stars appear to drift out of the field of view (FOV). You can nudge the dob base to keep what you're looking in the fov or you can later graduate to a tracking mount and view to your hearts content

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[Vox45]

Not silly !

The more you 'zoom in' the faster it will get out of the field of view. Not only is the earth spinning but the moon is also moving around the earth, orbiting. Unless you use a motor to compensate the rotation of the earth, you will have to follow manually the object you are looking at.

Keep at it ... it gets easier

[Mattscar]

I don't have a dob myself, but if you don't have the mount tightened up and allow the telescope room to move you can start to teach yourself to track what your looking at by hand. Theres advantages and disadvantages to using either  a motor, gears or by hand but each way can be used to see and track some amazing things out there

[Stargazer33]

There are no silly questions - only silly answers! The Earth is rotating at a speed of approximately 1670 kph at the equator. You need to multiply this by the cosine of your latitude to get the speed at your location. So, say you are at Greenwich, which is at 51 deg 28 minutes North. So 1670 x cos 51.28 = 1044.6 kph. At that speed anything that is at a fixed point relative to the Earth is going to drift across your field of view (fov). The higher the magnification the narrower your fov and so the faster the object will appear to drift.

[Qualia]

BTW: when you use your calculator along with Bryan's excellent description make sure that you set up the arguments for the trig functions in terms of degrees not radiane

[greencode]

Not silly !

The more you 'zoom in' the faster it will get out of the field of view. Not only is the earth spinning but the moon is also moving around the earth, orbiting. Unless you use a motor to compensate the rotation of the earth, you will have to follow manually the object you are looking at.

Keep at it ... it gets easier

Thanks, yep, it was my first night last night and I will definitely keep at it. I can see this getting quite addictive!

[brantuk]

It will drift a little slower with a lower magnification in your scope - eg 15mm or 20mm eyepiece. Fitting an RA motor and getting polar aligned is a great idea with the 130. It'll give you the ability to auto track at higher magnifications.

Woops - just realised you have the Heritage 130. Fitting a motor of course I was referring to an EQ mount. So you may be stuck with lower mag's for now.

[greencode]

It will drift a little slower with a lower magnification in your scope - eg 15mm or 20mm eyepiece. Fitting an RA motor and getting polar aligned is a great idea with the 130. It'll give you the ability to auto track at higher magnifications.

Woops - just realised you have the Heritage 130. Fitting a motor of course I was referring to an EQ mount. So you may be stuck with lower mag's for now.

And this is where you start to lose me "RA motor" and "getting polar aligned"?!

[brantuk]

Sorry - yes you can't polar align an alt/az scope nor fit an R/A motor. Your mount is altitude and azimuth on the Heritage. With an equatorial mount you would be able to track in right ascension (the natural track followed by the sky when the scope is aligned with the pole star). Hth

[NGC 1502]

With a non tracking mount ( like the Heritage 130 ) if you place your object to one side of the field of view, you can get the longest

look as the object drifts across. Keeping the magnification lower also helps - longer drift time.

This is also handy if you are letting others look through your scope. I did exactly this at a school stargazing session last evening, when we were fortunate to have clear skies.

Our club chairman, who has been into astronomy for decades, has a 130p. He got fed up faffing around with his go-to.

Regards, Ed.

[greencode]

With a non tracking mount ( like the Heritage 130 ) if you place your object to one side of the field of view, you can get the longest

look as the object drifts across. Keeping the magnification lower also helps - longer drift time.

This is also handy if you are letting others look through your scope. I did exactly this at a school stargazing session last evening, when we were fortunate to have clear skies.

Regards, Ed.

Ha, yes, I realised this last night when I was getting something in the perfect field of view only to then call somebody else to have a look at it and they said they couldn't see it. I thought they (and I) were going mad!!

[Matt Scunthorpe]

Its one of those little things that you will soon not even notice as you'll be an expert at nudging the dob to compensate, unlike myself, in which having never owned one, when I look through one and nudge it to keep it in view... they have to find it again for me.

Matt.

[AndyWB]

Ha, yes, I realised this last night when I was getting something in the perfect field of view only to then call somebody else to have a look at it and they said they couldn't see it. I thought they (and I) were going mad!!

Yeah, I find I have to 'lead the target' - point the scope at where the thing will be in a moment, and then get my friend to come and look. By the time they're sorted out, it's in the right place.

Normally, it's only a problem with things like planets - so at higher magnifications.