Conflicting Passover Info - Varies By Source

[KJ4YJG]

Greetings,

I'm very new to Sat work (thanks to field day) and over the past 24 hours I've consulted amsat.org, macdoppler, hamatdroid and a few other resources and they all report the passover times very differently. For instance Amsat.org would report AO-57 as coming up at my location at 14:12 and MacDoppler had it up around 14:50 and the others were off even more.

I'm just curious which resources are most accurate.

Thanks

Jon - KJ4YJG

[K6LCS]

>> ... amsat.org, MacDoppler, HamSatDroid ...

Either of these programs - IF UPDATED with current (i.e., within last week or two) Keplerian data and configured to your location - will give you accurate pass information.

SO ... If you have entered your grid square properly on the AMSAT.org pass prediction system, that data could be a "benchmark" for you. If you want to compare what an apps' live view shows for AO-27, SO-50 and/or the ISS, you can view the widget on my SAT SKEDS page ...

http://www.work-sat.com/Work-Sat/Sat_Skeds.html

Come back and let us know how this all works out!

Clint K6LCS
909-241-7666

[KJ4YJG]

Thanks Clint - I'm going to keep an eye but seeing as I downloaded both apps yesterday I had assumed the KEPS they downloaded were updated. I'll 2x check.

Thanks

[K0BAM]

I use heavensabove and it's pretty accurate. I always give myself 5 minutes or so before the pass.

[W5PFG]

When I "cross-check" my usual sources: Nova, Heavens-Above, and SatPC32, I almost never have a discrepancy worth mentioning. I get my Nova keps and SatPC32 keps from two different sources, intentionally. If I "miss" a pass and don't hear a bird, the first thing I go do is check the oscar.dcarr.org website and then double check the passes on my three trusted 3 sources. Rarely is there an issue but if there is, it's related to ISS (because they may have boosted the station higher and my keps are a day behind.)

[KX0Z]

I've always used www.heavens-above.com ands it has been very accurate.

[KS1G]

What Clint said. An error of 38 minutes sounds like one of the programs has slightly out of date element data. The data is updated about weekly, and you can go a week or 2 easily and not be too far off. Exception for ISS (space station), because it manuevers to reboost the orbit or to avoid debris.

Generally, the 3 main things that can mess you up are outdated data (Keplerian element sets), incorrect location, and incorrect time zone (if the program or website is converting between UTC and local time). As an example, your location from entering lattitude and longitude, or approximate using the center of your 4 or 6 character grid square. 6 charatcter grid square is more than sufficient, and 4 character is often close enough. Many programs and websites (amsat.org for example) do grid square to lat/lon conversion for you. Most of the programs will determine UTC offset for you from location if they can provide predictions in local time or UTC. Hamsatdroid updates directly from the phone's location data (GPS, cell network, etc.), but you have to tell it to do the update. All the programs have a menu to update element data from amsat.org, celestrack, or another source. Be aware that some of the sites use a different name for the satellite, such as the pre-launch name assigned by the satellite owner vs. the "Oscar" ID assigned after a successful launch. I get my data from amsat, so the names remain consistent. Some sites and programs can further adjust for height and for a minimum elevation above the horizon (to account for obstacles and surrounding terrain), but those are minor corrections you don't need to worry about now.

W5PFG has good advice on using the oscar.dcarr.org site to check "is the satellite active" in case it is off line or (AO-7) has switched modes.

Oh - "passover" time - it always begins at sundown on the 14 of Nissan, and during the Seder, is the time between the 1st cup of wine and "when do we eat"?! [sorry, I couldn't resist the pun!]

[W5PFG]

Oh - "passover" time - it always begins at sundown on the 14 of Nissan, and during the Seder, is the time between the 1st cup of wine and "when do we eat"?! [sorry, I couldn't resist the pun!]

Don't quit your day job!!!

Of the things you mentioned that usually messes people up, I find time plays a key factor. Many times the station is not calculating their local difference from UTC correctly or accommodating daylight savings time changes.

[WA9SVD]

I still use an old DOS program (STS Orbit Plus.) I also check Heavens-Above, and that has never been off by a degree or two, or a minute or two. STS Plus is still in agreement with H-A if I update the Keps. If a program is "off" by any significant amount (perhaps because of "above horizon" considerations) it's either worthless or hasn't been configured properly for tour location and time. Those are seemingly small errors than can make a big difference. The more accurate your location determination, the more accurate will be the predictions. For best accuracy, try to use a GPS if you can.

[KJ4NWQ]

Like the others, I use Heavens-Above for predictions. I have also been using ProSat for the iPhone and iPad out in the field. Works very well and is always accurate provided that the Keps have been updated recently.